The best option would be to go with the single password field, but ONLY if these are both applicable:
Your "forgot password" functionality is a smooth process. It should be a quick and easy process that makes resetting the password can happen effortlessly.
You give the user the option, with a checkbox or something, to make the password entry ...
It doesn't matter at all
Unless you have a strange user case with a 2 step flow (mail first / password second), the validation will come after the user completes both fields and submits the form. You can validate with autocomplete, but that would be a security issue, so I assume you will do it like everyone else.
About your disadvantages:
Check email only: ...