I have shot mine out to 1000yd (18" group), but, 600yd is more realistic. At 600yd I can get MOA groups and sometimes better if I am doing well that day, mainly wind reading.

At 100 I get less than .5" groups on a regular basis. 200yd 1" groups are also common.

Keep in mind that I have almost 3000 rounds on this barrel so it is quite a bit 'smoother' now. When new an MOA group was common. Took a few hundred rounds to 'settle down'. I'd do a good break in if I had a new one. Savage has one they recommend in their website FAQ.

Yes, the forward screw. But, if you are going to do one then it isn't a problem to do both. The rear one won't do much good unless you go to a steel trigger guard.

PS the long range loads that I shoot are 77gn Sierra Match Kings at 2800fps (23.5gn Varget).