I’m sure it’s all been said. I had two boys with 18 months between them, but don’t remember this sort of behaviour, throwing and other dangerous actions would be nipped in the bud as soon as it started unless it is a foam ball, but don’t let him chew it.
Things to try if you haven’t already.
Say NO loudly and firmly, as you would to a dog, a simple way to make him understand that something is unacceptable. eg throwing, but you can get a small child's ball ( a small beach ball) and play catch or football with it outside only. It will take him time to master this.
When out use reins if you can still get them.
Even go out when it’s wet or raining - wellies and mac, jumping in puddles is fun. Playgrounds are open now in our area.
When he has got rid of a bit of energy, play music -all sorts, easy listening, classical, sixties pop, show him how to dance or move to it, eg marching, jumping, rolling over.
Find unbreakable objects - plastic, wood, metal, and let him hit them with a wooden spoon and hear the different noises he can make. A toy like a dump truck he can load and tip up might keep him quiet for ages, indoors or out. You can let him use small unbreakable items to put into it such as balls of wool, small tins of food, plastic cartons etc.
Have some baby’s board books and let him snuggle up and turn the pages. With pictures of animals make the appropriate noise.
Has he learnt to count up to ten, know his colours?
I assume you have some age appropriate harmless plastic toys. If he throws things it is either frustration or temper, can you watch and work out why?
He may not understand why his mother is dumping him on you after he has presumably been at home with her. I sympathise with those that have no choice but to go out to work, the first few years of a child’s life are so precious, the foundation of who they will be is being laid.
Can you look after him in his own home sometimes if not always?
If necessary don’t be afraid to say that your health is not up to it, maybe your daughter can go part time.