Couple things you can do on the fsb pin. If it's not too loose you can stick the 3mm pin in a vise and bend it a little. That will give it tension.
If that isn't enough 1/8" is about 6 thousand bigger.
For the rsb before you demil the stubs ,pull the pin and stick it vertically in a heavy vise and use a big crescent wrench to twist it.
I wouldn't go off what you see by eye between the trunnion and sought base though.
Double check it on a good surface of the bottom of receiver in relation to the sight base.
Actually I'd probably wait till you have it in a new receiver.
Sometimes I like to sit the magwell on something rather than the front of the receiver.