Proof barrels don't save 2-3lbs... unless you're comparing a Proof to a Stainless heavy Varmint. A 24" Proof Sendero Light weighs 2lbs 14oz. A 24" Bartlein 2B standard sporter weighs 3lbs 4oz. You save less than 1/2lb with a Proof barrel compared to a sporter weight stainless barrel. You can also have a stainless barrel fluted and save 4-8oz. So there's really not a weight advantage with a Carbon barrel. Yes the Proof is stiffer and stays cooler longer for strings of shots. But for a hunting rifle, you shoot one or two times and it's over. It's not a bench rifle, especially a lightweight rifle. The Proof barrels are awesome and good barrels don't get me wrong. For me though, I'd rather use the $300-$400 savings and put that towards a carbon fiber stock.
As far as action truing goes, I have two semi custom 700 Remingtons and neither one of them has been fully blueprinted. One is a 1970s manufactured action, the other is about 6 years old. One is chambered in .284 Win/Norma the other is a .308 Norma Mag. They both shoot 3/8 MOA and both have Bartlein barrels. If you have the extra $250-350 to have the action trued, then go for it, it can't hurt. If you're on a budget, I wouldn't worry about it. I seriously doubt you'll be able to tell the difference on paper with a lightweight rifle if a blueprinted action made a difference or not.