Re: couple of questions
first off I think that looks like a nice bike to start with. if you are a tinker like I am then a Dax 2 stroke would most likely be fine as long do the job of installing it right the first time. Most the Problems I've seen most people have ( notice I said most not all ) had to do with there installs not the motor or kit. all that said if you are traveling a fair distance say over 10 miles one way every day and don't like to tinker go with a 4 stroke it will cost a little more but things like being able to just stop at a station and fill up will be nice.
as far as brakes first make sure there adjusted right then if it still don't feel good enough go to a bike store or search online and get the best you can find. if you are having to use your feet to stop it sounds like you need to adjust them first.