It sounds like your ISP is throttling transfers per connection. Your tech won't help you since he isn't aware of this, because usually this is implemented at ISP's datacenter and nobody but higher-ups and 'need to know' people know about it. Or he knows about this throttling but isn't allowed to talk about it.
the reason why your torrent transfers are not affected is probably because with bittorrent you are transferring to/from multiple peers at once and is constantly cycling through different peers.
Use bigstar's
http://trvx.com/itrafficmonitor/ to monitor your transfer speeds with different protocols as a proof that your ISP is throttling your connection. It's the same code that is in FlashFXP's transfer graph but monitors everything, not just ftp. Also see if you can find other users of your ISP that experience similar problems. See if there's a forum for your isp at
http://www.dslreports.com/forums/all?open=1