Thank you for that! It's just so hard when he's by the door or window and looks at me and gives me the most pitiful meow. Honestly, a part of me misses seeing him outside happily lazing about and the routine we had. But I know both of us will eventually be much happier with him indoors. I'm just very much a creature of habit, so it really affects me when something disrupts that. Even if it's a good change that I want. But I know he's not to that point yet and we both have to hang in there until he is. Like you said, it's a process. And I have to remember it won't be exactly like this for the next few weeks or months. It will gradually get better.This is normal as he is used to the outside but nevertheless, now that he is in and I mentioned a few post up, let him get use to being indoors as this will take awhile.
One thing you can do is distract him each time he goes to the windows and doors and meow. Talk to him and reassure him. Get a cat wand and start playing with him each time he does that and that'll take his mind off about the outside for awhile and do this till he does not ask to to let out.
Please do not blame yourself. What you are doing is best for him and he'll know it eventually. This is the usual process of time that you and Elwood have to go through and it's just a phase. Give it time and give up and now that he is in, never let him out else it'll be hard to get him in the next time or there may not be the next time.
If you have the time, give this thread a read and it may encourage you :- Feral in my garage. Do keep us posted of the progress but just don't give u