In the history of Losi 8th - I have had no issues with the brass collet. Your whole issue is you are not getting it tight enough.
To remove or install the flywheel, I use a nut driver and channel locks with a towel. Me personally, I do not use locktite. Not a drop on my engines. Personal preference. This is something I check once before the Quals and onces before the main. Make sure everythings tight.