Nick, welcome to the board.
He's a baby, and like all situations, someone does the training. Right now, he's training you. It's only been 4 days...calm down, you'll both be okay.
First, how long are you going to be able to give him all your attention? This matters because you need to tailor training to reality.
Second, what type of crate? It will be hard to actually hurt himself in a plastic crate.
Now for solving this. First you have done great. He likes the crate open, that's a good start. So you have something to build on!
Make the crate his the place for eating. Push the door closed, but open the second he finishes eating..lots of praise as you take him out.
Find a new toy he loves, or a chewy, again only in crate, door closed. Stay close, uptalk (happy high tone). At this point you're looking to get a couple of minutes, then slowly increase. Do this every hour or two ..you can even break his meals into 5 smaller ones so he is hungry and gets more training opportunities.
Once you have him comfortable with at least 5 minutes, the hard part starts. Walk out of the room where he can't see you but can hear you. Slowly increase the time. Then go out the door or take a shower.
Be strong. make sure he has pottied, give him a little food or maybe a kong you froze with a little cream cheese smeared inside. You now know he's not afraid of the crate, he's just trying to have his way. As hard as it sounds, do not go back in until he stops screaming. Gets quiet..go in casually and really praise him.
Most puppies want company all the time. Learning to entertain himself or sleep alone is critical for both of you.
Once you have time, start obedience work. A tired mind is a good mind.
These simple training lessons are all you need.