How should I deal with this neighbor?

The guy who lives next door to me was there when I moved in, three years ago this august. He seemed nice; had a dog, came over a fw times and welcomed me, etc.
The second summer he offered to cut my grass in exchange for taking care of his dog periodically. That worked out fairly well.
He told me more about himself than I’m generally comfortable with but i chalked it up to differences in upbringing.
Then he came over while drunk a few times. I don’t like being around drunk people for my own reasons, which I won’t get into here. He wrecked his truck while driving drunk. He told me he was on medication for mental issues, he was having girlfriend problems… all kinds of stuff that I’m not comfortable knowing. Then he came over and straight out asked me to sleep with him.
I freaked out and could not stop saying “no”. My brain disengaged and my mouth just kept saying “Oh, no. No no no no no no no. No. No no no no.” I don’t know how long. He came back a few days later and asked if he had come over and said anything stupid. He said that he gets all lovey when he’s drunk. I let that stand. Then I avoided him.
He left me a 16 oz can of beer and five one dollar bills in a used envelope this past Christmas. And he has come over twice recently to ask me for money.
He’s about 6’4”, close to 300 pounds. He fell off his bike about a month ago and stayed down on the ground. I finally called 911 because he didn’t get back up. Police were stupid about it, asking why I didn’t go try to help him. I feel like he’s too unpredictable.
My mom wants me to get pepper spray. Or a taser. I have NO idea what is appropriate here. If I tell him to leave me alone I feel like I’m really going to be in his crosshairs. I could take him down if I had to and saw him coming, but I’m not wanting to be in an adversarial relationship. I don’t want to hang out with him. How can I make him bug off WITHOUT bringing down the wrath?