Hello JenShepwood and Welcome to the Pulse!
I am very sorry for your loss and I hope we can offer some answers and provide some context that will prove useful. Please keep in mind that whatever information or advice I may offer is only based on my research and my experience and in my case, I freely admit that my current beliefs are entirely provisional; they are subject to change anytime I come across new or conflicting information. If Life and 'The Wider Reality' have taught me anything over the last 55 years, it is that my understanding of Reality will continue to necessarily expand and consider new perspectives.
The easy questions first. There are some really good books out there and each one I could recommend depending on what your current level of experience is at. A book offering a good, basic overview and some techniques would be 'Adventures Beyond the Body' by William Buhlman. But honestly, the best collection of material can be found right here at the Pulse, and it's free! You found one of the first, personalreality's 'How I Got Out...'. On the same Board is a good treatise on Sleep Paralysis and Lumaza's 'Exit Symptoms/Signposts'. And if you drop down to the blue stickies in the third Board you can try Xanth's 60 pager, Szaxx's 'Astral Blueprint' and check out Contenteo's map of the 'Conceptual Framework of the Astral' for an interesting visual.
Reading all this is good for at least a couple reasons: One, you get some fairly well confirmed concepts of what and how; Two, you get enough details impressed into your memory of what you might encounter as far as exit sensations and the likely environments you could find yourself in. Simply put, it is all good knowledge to have because we all encounter slightly different variations of all these Non-Physical phenomena and there is honestly no telling what you will encounter. You are already experiencing some of that in what you are describing.
Over the last few years, I have realized several personal maxims that relate to this form of consciousness exploration:
Stay open to pretty much everything
Know that you are always protected
Always go with the flow
Leave behind the 'Physical Reality' mindset and open yourself to an infinitely greater 'Non-physical' way of looking at your world and your experiences
Any experience that you have the opportunity to learn something is a valid experience
Everything can be expressed as Energy/Information/Consciousness
There are exceptions to pretty much everything
(This list can go on forever...

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Okay, here is a rough summary of the Out of Body experience available to most first-timers: You might be a natural at this and bypass all the preliminary stuff (you have already demonstrated this possibility). If you remember your dreams, if you actively participate in your dreams (Lucid Dreaming), then recognize that this is one form of OBE or Astral Projection. If this is the case, then look back over your life, especially your childhood and think about those exceptionally 'different' kinds of dreams you had; these were forms of OBE. Flying dreams? Dreams where you seemed to be tested? Rummaging through a house looking for something? Opening doors, checking rooms?
The 'classic' idea of an OBE is that you relax, get some vibrations and, like a ghost, float out of your physical body and go exploring your neighborhood and the local Universe. It can happen that way and often does initially. With some minor bickering amongst ourselves as to the true definition, we generally refer to this as a Physical Plane/Etheric/RTZ (Real Time Zone) kind of OBE. Most of us have experienced it. It's fun. It's also like watching a drunk guy at a party as he stumbles around exploring the concept of balance. There is a lot to learn in these experiences such as how you learn to control a Non-Physical energy body with conscious awareness. How you maintain balance, how you 'see', how you move, how you think...it's all quite new, confusing and a general hoot. There seem to be limitations to how far beyond our bedroom or house we can travel without losing awareness or encountering a necessary shift in consciousness.
Eventually our OBE experience does make a shift into a new realm of experience that is generally considered the Astral Plane and can be arguably sub-divided various ways, eg- the Personal Dream Zone, the Collective Dream Zone, and the Astral Proper which includes the Afterlife Regions where the majority of us spend our time in between lives on Earth or in other Dimensions or Realities...yeah.
Now...as humans currently existing on Earth, we don't automatically have a passport to freely travel to all these places anytime we choose; it is dependent on many factors such as our level of evolution, our 'spiritual maturity' and emotional control, our ability to operate with awareness that can sustain at that level of experiencing, our Intent and our 'need'.
A personal example: My dad died suddenly back in 2010 and I had a difficult time with it. I was having OBEs at the time but did not feel anywhere close to being emotionally capable of trying for a visit to check on him. Nonetheless the idea was simmering in my subconscious and one night I made an exit and the desire burst forth in a very spontaneous fashion. And somebody, I don't know who, took me to him. It was a very brief visit but I had my most basic desire or 'Intent' fulfilled, that was to see if he was okay. It was fuzzy, hazy, which indicated my inability to get my awareness 'up' to the required level...but it was enough. I said hello and asked if he was okay and he was. My 'guide' was a hazy blur to my immediate right but I knew instinctively what he was.
I am incredibly grateful for that experience and it also served as a huge confirmation to all this.
Beyond the RTZ and Astral experiences are what can be provisionally defined as Mental and Higher Level experiences. Maybe you have had some of these; many of us have in various forms. They can be visual or simply mental constructs, some literally formless and defying clear definition. They begin to defy description; language fails us.
Now to the more pertinent questions and I am sure some knowledgeable others will contribute.
Was that your husband? Maybe, but really you are the only person to answer that. If the connection between you two was that strong, then certainly it is possible. Maybe a good question to ask is 'Is he the type of guy/husband who would stick around to keep up that connection?' Along with that, do you really, passionately want to keep that connection? If the answer is a resounding yes, then maybe you two can keep a connection open. What you do with that is up to you (two).

Keep in mind that the general trend of the Universe is that we always are moving on to the next phase...there will always be time to catch up with one another at a later date. But then again...Rule #20 something says that there are exceptions to every rule...
I hope that gives some useful ideas to consider, others will chime in. We are all sharing and dare-ing.
Peace
PS T-Man beat me to the first response and he gave good advice!