PV stands for Point Value. When you face a Mecha with higher PV, you get moar XP, and vice versa, facing a Mecha with lower PV means you get less XP.
Everything has PV, even the player and individual NPCs/monsters, with the same rules; fighting a rat with a full set of cyberware, cyber armor, and an energy sword will give almost nothing.
The PV of any given item is calculated differently depending on what kind of item it is, a weapon's PV is based on it's stats i.e. Damage, range, accuracy, etc; whereas a shield's PV is dependant on its size, defense bonus/malus, and whether it's an energy shield. In general, the more expensive an item/mecha is, the higher its PV.
BV is burst value, which is how many much dakka is sent out per attack. So a BV:5 attack fires 5 shots (And uses 5x as much ammo/energy) in a single attack. BV doesn't give any additional bonus/malus aside from having multiple attacks.
Also, aimed attacks with a weapon always reduces BV to 1.
I think my knife broke after one fight and my rifle broke after like four shots. Is this normal or did I do something strange? Fighting fungal scavengers with no real skill or weapons isn't very fun.
AFAIK, weapons never break from use (Though parts can get damaged from attacks, including weapons; but this usually only happens in Mecha combat). It's most likely you're suffering from cooldown; which is dictated by the weapon's SPD. Also remember that ranged weaponry needs ammunition/energy. Thrown weapons will obviously need to be picked up again unless it has the RETURNING modifier token.
On a side note: The DC of unarmed attacks is based on your character's starting Body stat. So if your character started out a super-weakling with DC1 kick/punch, he/she will still have DC1 kicks/punches even with super-ultra-mega cyberware/equipment to boost his/her body stat to 50.
Is development stopped? I've been back to the official site and forum a few times, and it seems Mr. Hewitt is nowhere to be found... he was supposed to be making big changes to GH2's engine.
I think he's on "indefinite hiatus", I haven't heard a peep since the GH:Arena "demo" came out.