Ask him, by letter, "The hay will be $X. Do you want to send me a check, or should I deduct that amount from my next rent payment?" Then await his reply. If he says, "Take it out of the rent", with your next (reduced) rent check you can include a letter, "Pursuant to our agreement, I have deducted the cost of the hay from the rent." Keep copies of the correspondence for your records.
The access thing... You're either going to have to put your foot down, or live with the status quo. Allowing the owner access would normally be interpreted as a very different thing from allowing access to the owner's friends and family, or allowing access to other tenants.

