To be fair, the gravity thing is pretty hard to fix. You can imagine putting rotating sunshield/mirrors into orbit to fix the day/night/temperature problem, but mass is mass.
The Earth weighs more than everything else between the sun and Jupiter combined, and Venus is 80% of that.
"Until then, it's all just (un)educated guesses. "
We know that long time weightlessness causes damage, so 38% of earths gravity will likely have some bad effect, too. This is not just wildly speculating. But yes, for finding out, whether humans still can bear it, we will have to find out and there is no shortage of volunteers.
The Earth weighs more than everything else between the sun and Jupiter combined, and Venus is 80% of that.