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What would the optimal max bet be for me to make the most money with the least variance?


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Doesn't matter at all. Neither EV nor variance is affected by bet size.

You need to make sure that your bank can handle the action. Assuming, for example, that you're expecting a hold of 2.5% and you want a 99% chance to make it, you're looking at covering the loss of roughly 1200 deals.

From there you can do the math:
1200 deals * 4 hands * $5 max = $24,000

In real life, you're probably not going to need that much at once:

Let's say, instead that you're playing for 4 hour sessions at 60 hands per hour.
That's still only 240 deals, at a loss of $20 per deal, you're obviously covered using 240*40=$4800. (You could actually lose money more quickly than that due to doubling and blackjacks, but that's still a very conservative estimate.)

For more information on how big a bet you want to allow, you might want to look into bankroll management, "risk of ruin", and "Kelly Betting."