The SA XD .45's were notorious for not working with semi-wadcutters at least for me anyway. Do the new 5.25 .45's offer any improvement? If not, would it help to get the chamber reamed?
You also might check out Ready Tactical. You also might check out Red Dot Shooting-they carry a large inventory of Blade Tech holsters-may even have the one you are buying from Blade Tech.
I guess unless you can find one elsewhere you'll just have to wait until he has some more made. Did he give you a list of the vendors he uses to sell the mag releases?
Mitchell Custom on their webpage indicates they have them and are ready to ship. However, I don't know if they are out and forgot to update their webpage: http://bulletworks.com/Mag_catch.html Or is the mag catch different than the mag release?
Try lowering the powder die little by little until you get the necessary bell. The sizing die has nothing to do with the bell. What are you using in Station 2?