ideal time is late on saturday:
assuming it's 72 hours, this will give you:
both bonus weekend pack (sat and sun)
sun, mon, tuesday fox (note, it need to start on saturday after fox hour, so it last to tuesday after fox hour) for the 10% boost
sun, mon, tuesday sage/masuri (with a bit of extra ninja stat)

sat, sun, mon, tuesday survival. Note, if you are greedy, you can reset survival on friday and NOT do it, this will allow extra coins. (note holding friday survival will be penalized by unable to sweep, however, as you missed a day)

and monday pot for instance sweep bonus day.

Not sure. The reason you lose sweep is because sweep requires full clear the previous day, and if you hold it, you obivously didn't full clear. So I suspect you wont be able to

in that case, early on sunday then....
personally I value the extra fox at tuesday more than the "weekend reward" of saturday. Also 1 less set of survival....