Alternate fingerings are ok. I usually try the given fingerings first, but sometimes find an alternative is better for me - I believe that is valid learning.
There isn’t a limit on how long to take for posting, normally it would be within the month, but around exam time the priority has to be the exam.
I would echo Mike and say it’s about what we achieve compared to where we started that’s important. I, for example, will never achieve the fluidity and musicality that Ken and Mike achieve, but my personal target was to improve my sight reading and familiarity with the higher positions; for that reason I never memorise a piece.
I’ll give some thought to the legato, but for starters I would suggest working on a small section of, say, Nesta Rua playing it very slowly and practicing changing from one note to the next as quickly as possible, then slowly increasing speed. Scales can also help.