I'm stuck at Platinum 2 as I do not gamble a lot for almost a year now so I have no idea what will you get for reaching Plat 4 but I have heard that the level up bonus is indeed $1,600. For sure it does not make sense if you force yourself to wager $1 million just for the level up bonus, that's why it is better to play normal and let our progress for the next level move naturally. We may force ourselves to wager more once we are close to the next level, lets say 5% left to level up.
Stuck is not too bad because at least you are not deranked. Moreover, gambling responsibly, not gamnbling to hunt for badges, ranks, bonuses. Just gamble for fun and in events you like that has connections to what you like and support in real life.
Gambling to meet wagering requirement is a double-edged thing. Winners in wager contest know what they do and they win contest and don't lose their capital used in contest. But if you don't know what you do, the hidden edge go make it successfully, you will lose capital.