Are you depositing your pay in the bank?   

I built into my analysis of each property monthly deposits into that account to cover those contingencies.  

If I think about canceling the contract, I am very sure I'll not get the 10% earnest deposit I already paid.

It has to be secured before we can close, the reason we have requested a 50% deposit and other balance paid once closed.

(Q3)Security deposit is another area that I need clarifying on.

What happens to original security deposit from original 12mo lease?

You could ask for additional upfront deposits (double deposit, last months rent) if you're confident, but I wouldn't unless they were $100 or $200 off the 3 times rule.

Tell them you want your deposit back in full plus compensation for them breaking the lease and any extra costs you incurred (eg did you have a cancellation fee for movers-I doubt it as you said you didn't know when you planned to move in).

So, you definitely want to require a security deposit from them.Lastly, the $1250 in rent wired above is probably misleading.

However, I’d think most contracts have a deadline for performance where you can then terminate and get your earnest money deposit back and move on.