1. Bomb bays are missile weapons, even though they're classified as ballistic. It means they benefit from Missile Specialisation. However, in vanilla, they aren't available for sale aside from bugs, so they're only available on Piranha bombers, which benefit only from fighter skills.
3 & 7. I don't know the exact numbers, but I think Plasma Burn adds around 400 top speed, Burn drive adds 200 top speed and Plasma Jets add 125 top speed. Bomb bays inherit ship's speed when released.
4. Colossus Mk II has small ballistic turrets pointing to its sides.
5. Bombs from bomb bay have 150 hitpoints.
6. Missiles benefit from Ordnance Expertise as well, if that's what you're asking. Proximity Charges don't move on their own, meaning they can't benefit from ECCM in any way.
8. Proximity charges have 250 hitpoints.