mmmh... this may be a very dumb comment, especially if you're trying to move on, but what if you asked him first if you could delete him, saying you don't wanna seem like you're mad at him but it's just easier this way to move on.
I still have my last ex in my Facebook friends and luckily she doesn't go online all that much but when I saw pictures of her and her new boyfriend I seriously asked myself whether or not I shouldn't just send her a message and say that I'm sorry and that I don't want to seem rude but that I think not being friends on Facebook is a good solution. You just need to see it as how you handle it in real life. You don't see him in real life, because it's healthier. The same would apply on Facebook so not being friends could just mean you don't want to have info about him when you're trying to get him out of your heart.
I don't think you should be worried about looking stupid, it doesn't matter. I think you should focus on being sure it doesn't hurt him though, I mean if one day I looked for my ex on Facebook and realized she deleted me, I would be asking myself a lot of questions and it would hurt, I think.
If you think that's how you can move on, then do it and don't think about how you will look. However if you do, what I'm saying is don't hurt his feelings. Do it by seeing the situation under the opposite angle, how would you feel if he deleted you just like that?