During prohibition, it was much harder (and more expensive) to get beer (or liquor), and more liquor than beer was consumed at a considerably higher price. One outcome was significantly lower alcohol consumption and all that that means (lower deaths by cirrhosis, lower city drunkenness arrests).
If we take prohibition as an analogy, then sure, a dedicated criminal will still be able to get guns. However, a casual street-level criminal is going to have to work harder to get them because they're no longer available in the mall or from the pawn shop, and he's going to have to pay ten times as much to get one from Benny in the pool hall. That'll significantly reduce the number of guns out there, and that is what creates the environment and the expectation that results in cops shooting civilians.
Almost every appellate court below does in some capacity.
As does the original text of the Second Amendment (as you said.)
But again, how are you going to stop violent gang members from getting firearms without infringing on the law abiding?
Why not focus on the problem: rehabilitating the violent individuals + improving mental health, instead of hoplophobic, knee-jerk legislation.
Hasn't and won't in the foreseeable future come up for 5-6th, 8th, and 10-11th circuits. So with the score currently 1-4 at the appellate level and 0-4 with the Supremes, I don't find the Federal legal situation at all encouraging, since there's no state that forbids all unloaded movements of guns, I don't see much wiggle room for your "in some capacity".
Plus the law at all levels, as well as pretty much everyone but I suppose the criminal class, supports making it illegal for a "violent, law-breaking gang member" to possess a firearm if he's been convicted of a violent felony (well, any felony, but we all agree about the violent ones).