The balance needed to remove captcha is 2x your free roll winnings so it's possible you have won enough to need to deposit some more to get back to 2x.
The difficulty of reCapture is set by Google not Freebitco.in and it generally gets more difficult due to the number of requests from a specific IP address or browser. Also using an incognito window can help. Failing that if you don't do any for a while they get easier again.
I don't know if that's the case. Rewards have been dropping due to Bitcoin's increase and I recently deposited 80,000 from coinpot. I had no captcha before depositing that (and right afterwards too), so I don't think I've caught up in just a few days.
Also, if it is set by Google as you say, why is it so much easier for freedogecoin and the moon sites? I'm having one screen on those sites and even if I don't do it 100% correctly I pass, but I still can't pass the one on freebitco.in. I'm not doubting you, just wondering.