The lowest reward level is set to 0.2 dollar cent, which currently corresponds to 2 Satoshis. To increase this reward, you have to wager, as you said it. But if you only have a few Sat in the account you don't get the 2 Sat but only 1 Sat.
Some month ago the base Reward should be 3-4 Sat and for a short time I got 2 Sat per roll with ~15k Sat balance.
I guess the question depends heavily on how the rounding is applied. Maybe only 30k Sat is needed to get the full base reward. The 100$ dollar boundary is for activating the 1000% Sat bonus per roll if I remember correctly.
I believe it's not quite like you're saying, and yes, it's necessary to have deposited 100$ in BTC into the account to have the base reward, which at the moment is at 2 SAT per freeroll, and also unlocks the need to complete the CAPTCHA, and also unlocks access to all the bonuses that need to activate in rewards bonnus section,. To increase the base reward in the freeroll above 2SAT, it is necessary to bet large amounts and buy many lottery tickets, but nothing guarantees that it will be fixed, over time if you don't bet again, it goes back to base. Also, the more BTC deposited on the site and or the more you bet, the more Wheel of Fortune tickets you can redeem with the reward points you have.