I agree about trying a harness, that would be my first choice since you are in and apartment. If it was me, I would put my name on the manager's list to move as soon as a ground floor unit becomes available. They may let you move before your current lease is up. I'd definitely ask.
One of the ramp makers has a ramp that you can not only use to get the dog into the car, but can also lay in on steps. I can't find the right website right now and I'm getting ready for work. If you have a long flight you might need 2 of those. However, I think that's better for home use, not an apartment dweller, because at home you could leave it in place but in an apt. you'd have to keep bringing it out and putting it away.