I've got an MS in computer science, and the thing I've noticed missing the most when I've worked with people without a degree is not their programming/software engineering/etc. ability (they seem to pick that up naturally just by doing), but their theoretical computer science instead. Mind you, a lot of crappy schools don't teach that either, but it's really useful on occasion.
I'd say go through Knuth's The Art of Computer Programming in your spare time, it's got one of the widest coverages of that sort of stuff, and it's actually a lot more approachable and better written than a lot of the other similar textbooks out there. Assume it'll take you a while though.
I'm a self-taught programmer and theory is definitely my stumbling block. Also occasionally lingo...since my education is informal, there are sometimes things I haven't yet encountered that other people--particular CS grads--seem to already know.
I don't have any programming friends and so I also sometimes find it hard to keep up with a conversation that is using a large number of technical terms, as I have the mental overhead of converting those to ideas...it's not as natural as it could be with more practice.
I haven't read TAOCP but I have gone through a bit of SICP and I can recommend that. For slightly more practicality, I was doing it in Clojure, since that is more likely to be useful in the future than Scheme--for me, at least. The video course is on Youtube. I'd really like to get back at it and finish going through the entirety of it. Someday.
I am self taught as well and have tried studying CS on my own over the years. Do you mind sharing details on the particular topics you considered stumbling blocks? Thanks!
Since I have a good amount of actual development work, I'm doing Algorithms and Data Structures. Then I'll have a go at Nand to Tetris, since I have the book.
There's infinite room to grow from there. Copy the Trello board and it's a fun little game to get through. It's been fun and not as intimidating as you may think.
I'd say go through Knuth's The Art of Computer Programming in your spare time, it's got one of the widest coverages of that sort of stuff, and it's actually a lot more approachable and better written than a lot of the other similar textbooks out there. Assume it'll take you a while though.