Yeah, unity is freakin high for LRGB man. You should use 76 at most, but I would try Gain 0. You just don't have the dynamic range you need for LRGB. Unity is fine for NB, but you are indeed going to saturate FAST with LRGB filters.
I've used Gain 0, and swamped the read noise squared 50, 70, in some cases 100x. Swamp factor, assuming you at least get enough, becomes largely meaningless with LRGB even under moderate LP. You just need long-enough exposures that you aren't having to get a ton of them. If you are getting 30-60 second subs right now at unity, you should be at 120-240 seconds at Gain 0.
Yes, I know it's high (gain). But I shied back from losing faint objects in the noise and/or posterization. Also ran a test of 30s gain 139 vs. 60s gain 76. But honestly liked the 30s result better. But I'll re-do that, this thread made me suspicious that the 60s one might indeed have had too little dither positions. Might then as well do a 120s gain 0 run