Can I disable this functionality?

No, currently you cannot disable it. However, you can make the failed login threshold very large, for example, 999, and set the delay to zero.

Note that this could pose a security threat, so be careful with this!

Can I manually unlock an account?

No, currently you cannot manually unlock an account.

Do the other login modules have these features?

Perhaps; please refer to the documentation of that particular login module for more information.

The lockout takes much longer than
what is specified!

If users keep trying to log on before the unlock delay is passed, the unlock delay is reset to 0!