GunKraut

You don't need the late war stock. https://www.espeholt.dk/ac45.html

The metal thickness should be about 1.3 mm, the overall height 24 mm, max width 17 mm, overall length 20 mm, bottom radius 4 mm. The...

They could be G41/G43 or even MP44. Do you have a caliper on hand to measure height and also metal thickness? I can then look up and...

I'll take it!

WaA135 is Mauser. Mauser never made G/K43 mounts.

It's definitely missing the Picatinney rail for the LED flash light and the forward grip.

Fix the real problem, which obviously is bolt related, and don't monkey around with the hammer. I may have a spare bolt you can borrow...

Upper barrel band speed milled or sintered?

Oh, it's THAT guy! I would approach this rifle with utmost caution. Let the experts chime in.