As I mentioned, back then I didn't betting with normal spins method, so I always used the bonus buy feature on every spin. $6 for one bonus buy, and I do it repeatedly and often only get under 50% of the purchase. Well, in the end its doesn't matter how many bets I made, my control was really bad at that time. Even though I followed your method, with a bet of $0.2 per spin, my mindset at that time was "free spins = jackpot" LOL. So i think i will run till get the free spins, even I have to take a risk my balance is burned.
If we talk about Sweet Bonanza and its family members game, betting with normal spins is just like wasting money because there is almost no chance to win big with normal spins.
The wild multiplier comes in free spins only IIRC, still free spins in Sweet Bonanza is rare to give good final result.
If you did it with buy bonus most of the time, it is better than play normal spins but you did it wrong because you choose the wrong game
I think you would have much better results if you spend your money (the one you spent in Sweet Bonanza) in other pragmatic play with 5,000x max win.