So for #1, I have never been able to find the part alone (if anyone knows where to find the springs for the charging handles please let me know) but you'll need a new charging handle assembly because it seems like it's stretched out. In the future don't pull back on it so hard. I guess you could get a BCM or Stag Arms charging handle or whatever the "eleet oper8rs use" if you wanted. Or just find an OEM replacement. Once you separate the upper and lower you'll see how it's assembled back and how it actually releases the dust cover. The other option is to reverse how the spring is mounted on the dust cover so that it's constantly open which is something I've seen people do.
#2 Get a long screwdriver and screw in the screw inside the buffer tube, as well get an AR wrench (they should be able to be found for around $30-ish for a real steel one, don't get an airsoft one they're just as expensive and probably made of worse materials) and tighten the castle nut.
#3 Also should be able to be solved with an AR wrench, basically take off the rails and hold back the delta ring while tightening the barrel nut using the AR wrench.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE