It is great to see you addressing the issues, and not giving up, as it can be confronting when you play with a group and realise the gap (A reality check) - and you have gone for the community band to sort it out. Great decision!
I am sure that you have also begun to realise that 3rd and fouth chairs in the community band can be around harmony more than melody, so it is still a test of the music reading skills and blending. You are on the right track, hang in there and the real pleasure is playing with a band; it makes it all gell - makes sense of the practice sessions.
There is a real respect for 3rd and fourth chairs in community bands, the realisation that not everyone needs to be a Lead player to make beautful music happen. And you can improve and aim for a higher chair as you progress. Definitely the right track for a comeback player. Hang in there, I sincerely wish you my best for the future growth on trumpet.