1. I have Syntace C2 aerobars on my road bike. Similar to the jammers. IMHO I don't think they are worth it for a sprint distance tri. The only real benefit for me on longer rides is the ability to stay aero in a comfortable'ish position. Staying in the drops for 30+ miles sucks. But it is doable with aerobars. Totally different story if you have a TT style bike of course. My answer applys to a road bike with clip ons.

2. Also IMO there is no subsitute for swimming. Swimming, unlike the other events is far more about form than muscle. I have done better with my swim by working on my stroke. Swimming isn't something you can "just do more' of and get better. I would advise if you aren't going to be able to have a lot of swimming time that you consider a refresher swim class closer to the event and then practice on your form. Luckily for a sprint the swim isn't all that long anyhow.

-D