I agree with Dumpster Diver 100%--what do you need to talk about??
Does your regulator work? Do you have enough air to get you and your buddy back to the surface safely while sharing air? Then you can do whatever you want and it should be fine. You could just stop swimming, close your eyes and meditate until you reach a lower pressure of air, and then surface.
Lets say your husband starts to swim into the cave, tries to light a stick of dynamite, tries to eat a cheap frozen pizza, is about to bump into an alligator...the signal for all of those situations is exactly the same: use your light to wave side to side quickly, or grab your buddy's leg, fin, arm, etc, and then tell them no. You could do that with a closed fist (technically means hold but they should get the clue) if they don't get that, then give them the middle finger
So other than the "don't do that!" signal, the only other communication you could possibly really need is a frantic "share air!" or a calm "lets surface."
In the meantime, if your dive plan is "swim around" then just follow whomever is swimming in front, look around, and relax. No need to communicate.
Part of the joy of diving is getting to spend 1-4 hours with someone you love, without having to say a single word to each other.
In other words why pay good money for a tank of air and all that gear to sit underwater writing notes to each other? I hope you understand that I'm trying to make light of it, but I really don't see the need for very much communication, especially after a little while, you and your husband will probably be almost to read each other's minds...once you realize how little you need to talk, and how much you can understand what the other will do because of how well you know each other, you'll leave that slate at home until you take a deco class, and then you'll probably want a wrist slate that isn't easy to pass back and forth anyways
I'm sure that diving is for you, everyone has bad dives. The topside fun of it all is very important. Some people dive very well with their significant others, other people don't do well with that stress. Try to find some other scuba friends to go diving with.
The Scubaboard Megadive at Ginnie Springs is coming up end of October, I attended a Megadive just after getting certified and made lifelong friends, and it really helped me get into diving as a major hobby. If you can stop by, even if you can't camp, I'm sure you'd love the Galaxy dive!
And living in Florida, come make a weekend of it at Blue Heron Bridge sometime. Shallow, warm (right now!), and stuff to see. But, if you are worried about communicating as you swim around a giant circle, work on that before you go to BHB, it's a larger, spread out site, and if you aren't comfortable following someone or being followed, without talking about it during the dive, you'll be frustrated. Of course the best would be hiring a guide to dive there the first time to relieve that stress.