Problem adding shower to clawfoot

Purchased a faucet and shower kit for a vintage clawfoot. Installed the faucet w/out issue, but when I added the shower riser, the angle on it is way too steep. It rises away from the center of the tub at 30+ degrees. I need this to run vertical to tie into the surround.

What am I doing wrong?

Might be that you're not doing anything wrong. I've had the same experience, caused by improperly made parts. This was an $800. faucet/shower set, and
the supplier would not give satisfaction. There are clawfoot shower sets available where the shower riser has a swivel fitting at the bottom, so this problem
can not arise. You might want to ditch/return what you have and get one of those.

There is no standard on the angle of the tub wall, and if the kit relies on that and there's no adjustment, the shower riser won't be vertical.