Well I don't think you're going to damage him :) I know it feels that way, but we've all been there. It's an adjustment period is all. I had 2 who clung and one who cried.
My Mom was a kindergarten teacher for her whole career. In the summers, I helped her with a preschool program like a little morning summer camp. The kids do adjust as soon as their mommies/daddies leave, and you get them involved in an activity like play dough. I was that person who would take them by the hand and distract them while their parents left. The sniffles dried up and they were oblivious that their parents had just left. It's true, they are absolutely fine.
What's hard in your case is there is just one and she probably can't do that. So it just seems worse. I bet when the kids all arrive that she says Ok kiddos, and gets them involved and it's just fine.
Maybe you could time your drop off to be first - so she could have that one on one time just at the beginning? Or time it so he arrives with a new little buddy? Or send him with a toy he loves so he has a comfort object? There are so many ways to help him adjust. There could be a special toy he goes to when he gets there. You could ask her for suggestions. I'm guessing since it's not an issue for her at all - it really isn't an issue once you leave. Trust me, if he was bawling, she'd want to come to a solution with you and be asking you for ideas. So take that as a good sign.
My crier used to cry when it was time to leave, so I knew it was an adjustment thing in the mornings only. He cried all through daycare. It was just the way he was. I had to develop a tough skin. It was hard! You can send him with a little lovey in his pocket (I did that with one of mine) - a tiny little reminder of mom. Whatever works. He will adjust though - it will get easier. My crier eventually just became a sniffler. I found ignoring him and talking to the teacher helped too - instead of focussing on him. I acted like it was the most normal thing in the world and that he was in good hands. I tried to be confident that this was a great thing without making a big deal.
I never did half and half days anywhere. I found just staying at one place best for mine (is that an option?), but never had that option. I did prefer preschool over in-home with babies once they were preschool age for sure so I think right move. He needs to be stimulated and that peer interaction will be great for him :) Stay strong momma!