I followed a very similar pattern. I got stuck at DOS 5 and BASIC. At the time, I had a C book but my 286 couldn't run the compiler. Also, I couldn't run Windows 3.1. So I stopped learning and picked up the electric guitar.
Like you, I've come back to it full force in my 30s. Programming has invaded my brain, and shapes the way I think. I have rekindled the excitement I felt as a child and I won't let go of it again.
The manual had some instructions for learning BASIC. I messed around with it for a few days, but never stuck with it long enough with it to have an epiphany. It was only when I got to college in my late teens that my eyes were opened to the possibilities of programming. Wish I taught myself to code instead of wasting time moping around during my school years!
I learned how to program BASIC on Vtech too. It was "Precomputer Power Pad Plus", and it had a similar blue top spiral bound manual. I wish I still had the print copy, but I found an electronic one here: http://www.vtechkids.com/_f/_pw/_manual/Precomputer_PowerPad... .
Like you, I've come back to it full force in my 30s. Programming has invaded my brain, and shapes the way I think. I have rekindled the excitement I felt as a child and I won't let go of it again.