First time pasture board for my horse?!?

Hi, I'm hoping somebody can help me. I have a twelve year old thoroughbred gelding that has had some lameness issue for the past eight months. My vet wants him put out to pasture and 'not to touch him' for three months to get rid of his hunter bump. (I can still feed him carrots and that kind of thing). My horse is an ex racehorse and always been in a stall although he does get turned out about eight hours a day. He hates bugs (he has had to be brought in early from turnout becuase he runs around so much) and is very spooky. I'm very concerned about if he is going to be ok in pasture board where he'll be out 24/7. There will be one other horse out there with him and a donkey. I also live in Illinois where the weather can be horrible... thunderstorms, tornadoes, hail, etc. Also, it sounds crazy but will he forget about me? I'm still going to see him as much as possible. Any advice from anybody would be great cause I've been a mess since I found out he'll have to be put out there. Thank you so much for your advice.