As for round count, switch to a stock with bottom metal or use a chassis for AICS mags. They come in 5 & 10 rd for 300WM.

Savage Action screws are easy to find. Here is a factory screw, but a 1/4-28 Buttonhead will work. 2” length, measure & cut to correct spec.

https://www.midwayusa.com/product/1005119685?pid=491568