Hey GG,
Not at all, its good that you show such concern for your tank. It is ok to change out the water as it will help keep the nutrient levels down. The live rock will ensure that there is a steady enough supply of ammonia that the bacterial colonies will not suffer from the change.
As JD points out the algae is a normal part of the cycle and it is going to be with you for a couple of months. Once the algae finally dies away completely then that signals the final completion of the Cycle.
You are going to have hundreds of these baby snails indefinately from now on. They are very beneficial and you shouldn't worry about them. The feather dusters you are seeing are likely feather worms (small dusters) and they are typical as well.
You are fine with leaving off testing until after the next change.
If you think your post is long then you haven't seen mine!

You usually can't shut me up!
HTH,
Aaron