I'd make sure he has a pal with him if you are keeping him in. Personally, unless the weather is evil, or he is bullied by the others and you have no other way of ensuring he gets to eat whatever food you put out, then I'd think he'd be better outside - but if he's a favourite I am sure you can judge whether he's happy indoors, or not.
Give him a few days for the fluke to get knocked on the head, then give him a toip quality chelated mineral drench. So long as he's eating and drinking and you are giving him the best of feed, there's not much else you can do at the moment.
If he doesn't show some improvement in a week or so, talk to your vet. There is some resistance to some of the fluke drugs now, and this year we have found that we needed to use one of the others besides Combinex/Fasinex (triclabendazole.) But I don't know how soon it would be safe to treat him with a different drug if the triclabendazole doesn't do the trick.
Good luck.