Hey Froggy62,
I'm the same way with guitar, give me a key, and then I just listen for changes. It seems like you know the keys, you just need to apply it to guitar. It's not as hard as you might think, for example if a song is in the key of A it will usually have at least the 1, 4, and 5 in it. In A thats the A chord, D chord, and the E chord. Even if you don't read music, you seem to know alot about it. I still think you should learn music and theory, but there's no reason you can't find other ways to apply what you already know while learning it.

When you do learn it, it will also be useful in your harp playing. I've had to go back several times and reteach myself to do something differently. I haven't had to in many years now, but I have had to do that alot in the past. Keep jamming, and try to devote a little time each day to the theory, and key progressions. You can even do this mostly in your head, and with or without a guitar in reach. Here's a quick example, and after the A progression I mentioned earlier you should see how it works. This formula can apply to any key, but there may be some changes in which chords work best.

Here's the key of G

1 2 3 4 5 6 7 8
G A B C D E F G

It kind of works like the alphabet, and just concentrate on the 1, 4, and 5 in each key. Saying this aloud, will help more than you know. It won't be long, and you'll start retaining this info. I was told a long time ago that I knew a lot that I didn't know I knew. After learning a little theory, and how to sight read music, I finally knew what they mean't. I'm not trying to burst your bubble, and I've heard my Dad say the KISS thing many times too. I've even used it myself a time or two, but once you start learning this it's simple too. when it finally clicks, it will be like a V-8 moment. This is only my opinion, and you can do what you want. There's a lot to learn that is complicated, but there is plenty to learn that's easy to comprehend. Learning that stuff can really help your progress, and even make the complicated stuff easier to learn.

Let me know if you have any questions about any of this, and happy new year to you.