https://www.armalite.com/SACItem.aspx?Item=EA1090
https://www.armalite.com/SACItem.aspx?Item=AR10REKIT02
Call them they don't list the spring on the web separate. The right spring and proper weight buffer is the first step on solving your problems.
You have a carbine length buffer tube.
If you are not wanting an adjustable stock this one will work.
https://magpul.com/moe-fixed-carbine-stock-mil-spec.html?mp_global_color=undefined
I was having similar issues w/my 6.5 creedmoor. I shitched the ejector to this and the problem went away.
https://www.kakindustry.com/lr-308-parts/308-upper-parts/308-bcg-and-spare-parts/kak-bcg-ejector-308
KNS is who makes the retaining pins I use. Solid w/split ends.
https://www.joeboboutfitters.com/KNS-Perma-Pin-Firing-Pin-Retainer-p/kns-perma.htm
That is the one for the AR15 but they also make them for the large frame guns.
The 140 American Gunner shoots well in my creedmoor as well. The cheap Winchester 125 gr also shoots well. Not as well as the American Gunner but still sub MOA.