Well, your little boy is not going to meet your needs in this matter, so you'll have to meet his.
You could do things outdoors as a family. Your husband could go along with your boy's desires, dubbing him a valued assistant and saying, "All right, you watch me take the trash out and see if I do it before you can count to..." You could get your son to help Daddy with some of the things he does, both in and out of the house; when he grows more confident in this, perhaps they could each take a chore and meet when both chores are done (or when a timer goes off.) You could arrange outdoor play dates with his friends at your house and at his friends' houses.
You could possibly (depends on the boy!) ask him, "What would be the worst thing about being outside by yourself?" If he says it's because he's afraid someone could get him, you could teach him the plan for what to do if a stranger comes into the yard. If he's afraid of being locked out, show him how a lock works (he might find it interesting) and give him a back door key to carry in his pocket.
You could also ask advice from a counselor on this matter. Yes, several months is a long time, but then your boy has had a VERY bad scare.