Limit Apache (thread) Connections Per Request

I've been having trouble the past few days with someone who's been "attacking" my site so to speak by continuously downloading very large files with as many connections as (he) can open. I operate a large downloads site for computer games, this person has selected the largest files (like 400-500MB). Not sure of the real intent other than to clog up my bandwidth capacity. Also he appears to be using proxies since as soon as I ban one, another shows up seeminly from China.

Anyway, I have mod_bw and I've limited the number of connections in the downloads area to 2. While that works ok, his tool uses threads like a download manager would and he's using up 30-40 child threads for his 2 file downloads.

So 2 questions,

Is there anyway to not only limit file downloads to 2, but limit the number of connections per request? Many of my visitors do use download managers and I'd like for them to continue using them but use a reasonable number of threads like 6 or 8, but not 30.

Also, is there a way to restrict access to someone using a proxy?