I need serious help!

[Sigoura Edge]

I purchased a property at 58k last summer owner financing. The agreement was 1,000 for 12 months then $600 until the debt is paid. My income shifted so they’re was 3 months that I paid $600 which the man said it was okay. Last week (3 months later) he told me that I owed him $1200 which was the $400 balances from the $1000 each month. I paid him. Now he is saying I owe him $300 in late fees. We agreed to the 5th of every month, and my deed states that I have 10 days from the due date before any late fees are accessed. He says it’s mandatory that I show him taxes paid and insurance on the property. I was never told this about the insurance. But I read the deed and it says if anything happens to the property I give him the money from my insurance company and he’s the power attorney of my property until it’s paid off. Is this fair? Help!!