That is a lot of cracks but it is still repairable. It will take a lot of beveling (V bevel equally from both sides ) and welding but it can be done if you have a welding machine and grinders. I would drill a 1/4" hole at the end of each crack where it is still running into the wheel, then grind a V bevel from each side so that you have nearly full grind thru but leave enough metal for the first weld bead so you don't burn completely thru. Then finish grinding from the other side till you remove all the crack and reach the new weld metal and then weld the back side.
Do this for each crack. The smaller pieces, weld up the crack from one side after making a small groove and then back grind to good metal from the other side and weld it up. I would use all E7018 stick electrodes and run them fairly hot to assure good tie-ins and no trapped slag.
Keep the metal cooled around the rim so it never gets hotter than you can touch with your bare hand and I think you can do this without removing the tire.
If you do this yourself, it will be much cheaper than a new rim but if you have to have a shop do it, it would likely be cheaper to just buy a new rim, assuming you can find one.