great progress on the pullups!
one thing i have found that has helped me, is practice! when i first started doing pull-ups i could do maybe 5. so i would do a set of 5 then a set of 3 then a set of 3 again. i kept at it and started doing negitives on my last pull up. i also used the
assisted pull-up machine for a while. i kept working at it trying to add an extra pull-up every couple weeks, it's worked for me and now i can do 10-15 pull-ups in a set. the second set i do 8-10 and the third set i do about 8.
good luck, it sounds like you've already made some progress!