So much for their "default setup".
In defense of AMP they did not post any "personal information" about you other than the size you've admitted to taking. TBH I don't get the $800/car without any limits posted on their site. It's what's kept me from funding an AMP account.
Ironically, they are a lot more conservative that I'd thought, although nothing is in writing. I would be irked as well if the $800 offer was a bait and switch.
I'd counter with whatever solves for 100 points of intraday risk on ES (200 lot per mil; $5K per) and call it a day. You're not going to be satisfied with any of the major FCMs moving that size for that cost-structure.
I had $2MM with Refco in 2003 and they would go to PHONE ONLY when vol rallied. They were the only house that offered eccotrader at the time. I moved to Stone before Refco's blowup.