I need to send some bitcoins, but Im not sure how long I must wait. I thought it was safe when the first two transactions disappeared, but that wasnt the case. Based on what happened before, Im assuming if I try again, the same thing will happen, since there is still an unconfirmed transaction. So how long should I wait before I try again? When will the double spend transactions disappear from my wallet?
Only blockchain.info knows. I suggest you contact their support and ask.
I suggest you move to proper wallet software like Bitcoin Core. It may be burdensome considering synchronizing and hardware use, but at least you can be sure that transactions are working 100% as intended. Normally 2 days wait time should lead to automatic reappearance of transactions with insufficient fees. Blockchain.info seems to be mixing things up here.