Regarding your balance, it looks like you still have a long position of +0.2 mBTC. If you close this position (by sending a sell order) your balance should be unfrozen (+/- your profits). You say you tried to cancel your position, what did you try to do? Maybe you can help us make it more intuitive.
I can't sell something I don't have because I went to cancel open order and I think you should improve interface and make it more intuitive.
Maybe adding some tutorial page with instructions would help with this.
One more issue I have today is that I can't place any order and I an getting error that something went wrong and that I should contact support:

Future tokens were just meant as a (small) thank you gift! If we do well these may be worth 100x-1000x in the future, but you don't need them for trading (in the future they'll give trading fee discounts and other benefits). Thanks for trying out, hope to see you coming back to close your position and trade more

I would prefer to get a real Bitcoin as a gift, instead of some new speculative token that may never get listed on any exchanges.
what is the point of testnet coins here? testnet is moslty to test the new dev of the main network just like bitcoin main network with zero economic value.
You can give the user any amount as it is an update of the database and after he succeeds in successfully trying the platform, that balance can be replaced with your free tokens.
You can withdraw those coins to your own testnet BTC wallet, you can also deposit, and it's obviously done for testing, nobody is crazy enough to test something like this with real Bitcoin.