I would def recommend the DA. Had a guy in our squad this past weekend with a ton of light strikes with a lightly sprung SAO SP-01. DA might have ignited most of those on a second strike
No, the gun will be fine. Many of us run 7pd springs in our open guns.
The recoil springs function is to compress and return the slide into battery. The gun can still fire once without a recoil spring in it.