You really need a GFCI breaker. Is that in your house box? If it isn't, then you should reconsider your decision.
Also, if you change your RIMS element from 110v 2000w to 220v 2000w, you reduce your load. i.e. from 16.67A at 120v to 8.33A at 240v.
And if you really wanted to run everything on the 50a circuit, change out your two 5500w elements for 4500w elements (these use 18.75A compared to the 23A for the 5500w elements) and you'll use something like 47A.