I'm pretty much in the same boat as the OP and I've been winging it off and on for around 20 years now!!
My theory knowledge was and still is extremely poor. Even though I have been able to hold my own in all the bands I've played in over the years, it's only in the last six months or so that I decided to get on board with a tutor in order to start building up my own theory knowledge.
"Unlearning what I've learnt" is exactly the phrase I have been using also and it's proving to be a complete bugger, and whilst I wouldn't say I'm much further along the road than I was six months ago, even already I can see things starting to fall into place.