1st, what's done is done, I'm sorry that you have to go through this painful process but you have to. Next time stick to more reputable platforms.
2nd, what the actual F? They SHOULD NOT ask for Telegram conversations whatsoever, that's against the law!
3rd, a good chunk of the crypto tokens have been through darknet wallets at least once and that IS NOT a reason to freeze your money.
4th, ONLY BANKS and electronic money institutions can ask for a SoF documents, not a crypto swapping platform like FF.
5th, at screenshot number 2, they say that a refund is only possible if you can provide them with evidence...WHICH AGAIN, IS AGAINST THE LAW! Even banks will send the money back to the originating address, no questions asked, if your "evidence" does not satisfy them, SO THEY CANNOT KEEP IT FROZEN!
Now to their Terms of Service, which are as predatory as they can be:
Point 7.8 says: "If you refuse to provide data about the origin of the funds sent or provide false data, and if the data you provide confirms your connection to criminal activity, FixedFloat has the right to freeze the funds for the subsequent return of funds to the victims with the assistance of law enforcement agencies."
They do not have proof that you got these funds through illicit means, for that reason they cannot get LEA's involved, HOWEVER, if I were you I'd file a complaint with Interpol as soon as possible.
Point 7.9 says: "In some cases, when for objective reasons the User cannot provide sufficient evidence of the source of the funds received, as well as in the case of a personal acquaintance of the sender with the alleged criminal who sent the funds to the User, as an exception, the User may be asked to undergo identity verification.", this one is already labeling the sender as a criminal, for which they have absolutely no proof to do so.
Fixedfloat is scammy and scummy, as someone who has worked in the blockchain investigation field in the past, with the information you have provided, there is absolutely no reason for them to freeze your funds! I say they want to keep your money and you should fight for it.
Worst thing is they force me now litterly force me to get my customer to reach to them i am calling him in middle of night on telegram and he is pissing me off for that and i bet he will say its your problem i think i will be first guy who killed himsef over being blocked his own money my luck is really fucked up i got job after 2 year being unemployed worked always below developler average payment and finnaly when i got experience and start to get reputation i get fucked on my first big payment job i will let you guys know what is status daily i contacted everyone i could and they are all as shocked as you are. i provided everyone proof and same thing i providoed to them it's just pointless they are like robots constantly saying one thing this is worst than CCP blocking money of people what the fuck is happening with world at this moment that always bat is broken on back of honest