extremely soft 2nd to 3rd shift

As for the shift kit, if it shifts like you like it now going from 1st to 2nd I'd leave it alone. Most shift kits affect the 1-2 shift far more than the 2-3 shift kit. Adjusting the front band may help the shift some but the front band is mostly for the 1-2 shift so it may not help much, unless it's way out of adjustment now. How I get a better 2-3 shift out of them is to adjust the line pressure up 2 turns and drill out a passage in the transfer plate that is for the front clutch feed. Here's the only problem, the rebuilder told you he did some tricks to it but what did he really do? He may have already turned up the line pressure and drilled the front clutch feed port. Or something else. Or he might not have done much at all. Hard to guess.