It sounds like you’re a month to month tenant (or are you on a year lease or?) from what I can tell. If so, he can provide you with 30 day notice to vacate the property. If you do not he can start the eviction process. He needs no reason to end your tenancy. If you’re on a year lease and it’s not specified in the lease no he cannot evict you or end your tenancy for this.

AFAIK he needed to provide you notice he was enter the yard as this was not an emergency.

Yes, you can lock the gate assuming you’re lease doesn’t state you can’t (I’d highly doubt it does).

If he attempts to evict you contact a real estate attorney ASAP (assuming he can’t just end your tenancy on a month to month lease…if so, be out by the specified date..this is totally legal on his part)