as long as your chain isn't slack, there's nothing wrong with using a masterlink on a fixed gear.

as long as the chain is straight, a little noise isn't gonna hurt anything. sometimes chains make noise when they're too tight as well, you should be able to wiggle it about 3/4" vertically.

if anything's questionable with the drivetrain, keep the brake. if you have any more fixed-specific issues, try the fixed gear/ss forum. many of us work on our own bikes. cheers.