Upgrading my Redcat Everest 10 - questions

[Notorious J]

Good morning everyone
I've had an Everest 10 crawler since summer 2020 and have done little to improve it. Couple of things I'd like some advice on.
One, I've seen crawler tires that are way more "flexible" then mine. Mine are too firm and that inhibits it's ability to climb jagged surfaces. Some suggestions of ones you use would be great.
Two, my rear drive shaft slips off the center output shaft all the time. I have tightened the set screw as hard as is possible, but that seems only temporary. Any quick fixes for this?
Last, and a little over generalized, why do people add weight to crawlers? Is it simply to lower the center of gravity?

 

[monstertruckier15]

Blue Loctite for all screws in metal

 

[Notorious J]

Blue Loctite for all screws in metal

Thanks for that but it's not the screw backing out. It literally just stops grabbing into the metal output shaft. Worth it to just replace the set screw?

 

[monstertruckier15]

You can drill a dimple on the output shaft so the screw will grab more and use Loctite.