That is the worst of all worlds: TV size with Projector quality, cost, complexity.
Buy a 4K OLED 75" direct view for the same cost of a projector and screen and have much, much better quality viewing.
Well, I wouldn't say quite the worst of all worlds.
NOTE he's asking about something in the 70-75" **width** range, not 70-75" diagonal as most seem to misread/assume. That actually comes out to 80-85" diagonal instead. Still very doable w/ flat panels nowadays of course, but it does cost substantially more than 70-75" diagonal.
Honestly, if I were him and wanna bother going FP, I'd go fair bit bigger than that since it seems very doable w/ his space -- somewhere at least 100" diagonal should be doable me thinks. OTOH, he'd likely be able to achieve a somewhat brighter image if he keeps it smaller, so...
_Man_