First of all, you had EVERY right to be scared. Your intuition (and basic intelligence) was sending you strong signals. You then did your research and validated your fears - He is a CONVICTED SEX OFFENDER. You have EVERY RIGHT to make sure he never enters your home or comes near you again.

This is what I would do in your shoes (which does not make it necessarily the right thing to do):

1) Yes, cancel that appointment.
2) Be assertive with your landlord in the following ways:

- Let them know he is a sex offender and you have the right to refuse allowing him into your home.
- Let them know he made you extremely uncomfortable with his body language and by divulging too much personal information.
- Request strongly that your landlord find a different maintenance person to fix things in your neighborhood.
- Assertively request that they no longer do business with this man, without mentioning you at all, but on the premise that they do not hire sex offenders. They can 'fire' him without mentioning you at all; let them know that.

You have every right to have been uncomfortable, to trust your instincts in this case, and to refuse to allow him in again.