What it the strongest, stiffest, and most weather proof hair gel made at this time(i have a big moha

Super-glue.

I'm not kidding, we used this in the late 70s and early 80s to ensure a permanent doo. 2nd to that, use Knox unflavored gelatin. Still not that brave, try the crappiest cheapest hair spray you can find and use a mask because you'll want to thoroughly lacquer the hair into position. At the time, I never found any of the gels to provide sufficient hold, perhaps they've improved since then.

What it the strongest, stiffest, and most weather proof hair gel made at this time(i have a big mohawk)?

try Elmer's wood glue. Or a ton of hairspray like someone else said. Just make sure it's aerosol, not the pump kind, and go for something that says super/maximum/ultra hold.