I really feel for you, you have your hands full. Hugs to you!
Well, maybe, try having a cabinet JUST for him. Put things in it that are safe and fun... and even perhaps empty bottles/containers etc. from "real" products (but empty it and clean it out first) and then put colored water in it or something. I don't know if this well help... but maybe worth a try??? Or, maybe have a room just for him.... to mess up and play in??? If you have an extra space/room that is. And perhaps put in just hard flooring... versus a carpet... so it's easier clean up??? I know, but that costs money too...
Have you tried reward charts? Or any kind of "incentive" motivational tools? Maybe that will work with him.
He's 4 years old already.... and usually by then, they do have some sort of impulse control. Is he attending any kind of school???? How is his behavior there? Perhaps ask the teachers for any kind of tips???
I agree, it is very dangerous... and no one has eyes in the back of their head to watch his every move. What if he ingests something and ends up in the ER. Does he even understand "cause and effect?" Usually, kids this age understand "danger."
Who watches him during the day when you work? How is his behavior with that person or at that place???
Can he listen to directions?
Perhaps, get a book on "spirited" children... or "how to discipline your spirited child" etc. There are lots on Amazon.com
Sorry I don't have any magic answers, you've probably tried everything already. I really give you credit for managing your children/household being a single parent... you really seem to be doing your best.
MAYBE, send him to counseling? He seems to have trouble listening and then doing and is "destructive."
All the best and take care,