Halberd Question

If I have a barbarian with polearm master using a halberd, do I benefit from the rage damage bonus as well as the cleave feature on the bonus action attack feature gained through polearm master if I have not yet used the cleave feature on my main attack? 

Sure. Cleave can be used when you "hit a creature with a melee attack roll using this weapon", which is what you're doing when you make that extra bonus action attack. You can only use Cleave once per turn, but it doesn't have to be on the first attack you make on a turn. (The first attack would probably be preferable in this case, since it deals more damage, but if that attack misses you might want to use it on the bonus action attack.)

The Barbarian Rage damage bonus applies to any attack roll made using Strength, which would include both the main attack and the extra bonus action attack in this case. There is no per-turn limit on this, so you get that extra damage on both attacks.