Gas tube length is good, recoil systems is goor, except for maybe the spring. Armalite EA-1095 spring or Sprinco Red spring will definitely do it.
All that's left is gas port diameter. With the proper gas port diameter, that gun will run. Like a sewing machine.
Let me look at one that I have that's similar, check it's gas port diameter. I'll tell you now, this I know... 18" midlength gas, 0.750 journal, needs 0.085" port. 16" midlength gas, 0.750" journal, needs closer to 0.090" port. With your longer-than-midlength gas tube, you can come down a little from there, but I'll say you need 0.085" port, minimum. Maybe a little more.
That gas port needs to be drilled out. 0.078" just isn't enough.