Do I keep my guns through later prestiges with their levels still there and not reset?

Solution 1:

The unlock token will keep your gear (weapon in this case) unlocked for all future prestiges, but it will not keep the experience, camo, attachments, etc for that weapon unlocked. Those you will have to re-acquire on each prestige. For more info, read here.

Unlock Gear (can be weapons, equipment, perks, deathstreaks, available at 1st Prestige, also they will be carried on through future prestige levels. Unlocked weapons will be reset to weapon level 1 upon prestiging. All unlocked attachments and camouflages are lost in this process, except winter camo)

Solution 2:

The item will stay with you for all your prestiges (to prestige 10). It will not lock after you prestige and is not limited to just 1 prestige.