I agree that 7 kills in a bomber seems high. (My record is actually 18 kills, but 10 were ground targets (bombs on map room and VH) and 5 vulches with the forward guns.)
If you guys watch that film only 2 of the planes I killed actually took the time to set up a non-suicidal attack. Staga damaged the spit, and the f4u made the mistake of staying on my 6 for too long. If you noticed I was basically dead when two planes attacked at the same time. (This is more like real-life IMO.)
I should also mention that in the last 5 tours I probably have 50 kills of bombers to only maybe 3 or 4 deaths. (I know one tour I was 17 and 0, and that was in p51s and p47s - non cannon aircraft.) If you set the attack up properly bombers, and the b26 in particular are VERY EASY to kill.
Here's how I do it:
NEVER attack a bomber by coming up on it's 6 level. If you do that you deserve to get shot up.
On a b26 come in on the front beam and slightly below. He can't get a single gun on you then. If you miss, rather than pulling up, go right under him and then try to pop up shooting at underneath the cockpit or a wingroot. Another easy way to kill a b26 is from directly above them, the top turret only rotates up 45 degrees! Never HO a b26, they have 5 forward firing MGs, you will die.

A Lanc is the hardest bomber to kill, they can absorb tons of punishment. I prefer to approach them from above and in front. Always aim for the cockpit, rudder, or wingroot. (MG planes should aim for the cockpit.) I have a film of me attacking a lanc in an la7 where I landed 50+ cannon hits before the thing finally died. I was minorly damaged in the attack, and I was parked on his 6 most of the time.
A b17 is the hardest to approach properly. The best way is to come in from above and head on if possible. Make sure you are turning slightly to throw his lead off. On a b17 aiming for the tail is the easiest way to kill them I've found.
A tbm is easy to kill, their guns are practically worthless. Just don't overshoot and let them shoot at you. They are pretty nimble for a bomber.
An Il2, though tough, has a glass rudder and elevators. They also have no way to protect themselves from a low 6 attack.