Just guessing here but it seems like the rack for the breakers should be turned 90 degrees in the enclosure. The reason your "green is too big" is because the wires are WAY oversized for this single phase breaker apparatus. "A" phase would be the left, and "B" phase would be the right sides of the bus, but that's not written in stone or required. The multiple land bar attached to the bus ***'y would be the neutral bar, and the similar bus located away from the ***'y attached to the enclosure would be the ground.
Should there be electrical continuity between the ground and the neutral? I don't know, it depends on the scenario. Where's the first means of disconnect? Do you know what first means of disconnect means?
Really, not trying to be a **** here, but for the love of god, do some research and if you're going to send 240 volts into an enclosure, get an electrician. The conductors going into, and leaving the enclosure must be protected i.e. romex connectors.
Is that a joke?
Yes, "TRIP" the main breaker is one possibility. The other is burn your house down. You don't get to choose, though.

Facepalm indeed. I think the stat is 90 percent of house fires are electrical in cause. This is an accident waiting for a convenient venue.