1. Thinkorswim is primarily an options platform, and is very good for that. However, it is a shitty platform when it comes to futures and Forex.
2. You aren't going to find the type of leverage you seek with US-based brokerages. You can easily find that type of leverage outside the United States. My instincts tells me brokerages that offer that type of leverage tend to be very seedy, usually located in places such as Russia, Greece or the Caribbean. I could be totally wrong. But that's what my instincts tell me.
There was a time when I briefly considered Forex, and came across this brokerage offering 1000:1 leverage.
https://www.tradersway.com/
I cannot vouch for them, so please proceed with caution.