Congrats on the spawning and i know just where your coming from excpt i have probably closer to 500 , mine are now aboutn 3 months old and doing very nicely, now for your questions.
1, if you crusg the flake up VERY fine you can start at about 3 weeks i found without any fear of any great numbers , introduce it along with the other food then stop the egg yolk, and later the brine shrimp too if you want too but they will love that even as adults.
2,I do very slow/low pressure syphoning into a bucket through a fine mess net so any babies get gentlely dropped into the net then returned asap t the tank but if your careful not many get sucked up.
3, i'd leave them to grow there until there at least 1cm then i'd say pretty safe to move them but do it it stages, say 50 one day leave it a week ,then 50 more till there over moved over , gives the filter time to cope with the extra numbers.
Good luck there very pretty fish