Terminology and Application Questions

[Rabid_Explosions (PSN: iPayUrFrenZ)]

Some of these questions are embarrassingly simple, yet I want confirmation.

1. Heavy Weapons refer only to Rocket Launchers, right?
2. What weapons/items, aside from grenades, get boosted by a boost to Grenade Damage? Is it just grenades or any weapon that causes splash damage?
3. Handling refers to recoil, right?
4. Do Eridian Barrels on guns have a specific effect or does it vary depending on weapon type and/or manufacturer?

Thanks in advance.