@BryanM beat me to it, but yes, I think you'll be fine, but be careful being that you're in an apartment. I'm pretty sure the people under you will be upset if you flood their unit with saltwater lol!
But seriously, I would think you're fine. And if your floor could handle a 75 gallon tank, but adding a 29 gallon sump (which would run at half volume or less) pushes you over the weight limit, then I wouldn't run the tank at all.
I don't know if you're in a house that's been converted or a high rise type building, but if you're in the former and know which way the floor joists run, placing your tank perpendicular to the joists will help, as will placing your tank up against a load bearing wall.
If you're in a high-rise type building, I'd be willing to bet you're fine. Not to be rude or mean or anything of the sort, but this is 'Merica, and we're 'Mericans, and you'd have to plan for a few 300+ pound people inhabiting that unit. If a few of them came together to talk, that's a 75 gallon tank right there, weight-wise. Again, no disrespected to anyone at all. I freely admit I have to shake off some of last year's extra calories. I'm just reasoning that a 75 gallon tank is likely fine in your situation :-)
And to answer your question SUMP before a canister, all day, everyday, in my opinion :-)
Good luck with your build!
