Are you a Tarantula hobbyist? If so, we invite you to join our community! Once you join you'll be able to post messages, upload pictures of your pets and enclosures and chat with other Tarantula enthusiasts. Sign up today!
Sounds like its getting close. In the wild they would probably fall to their death but in captivity they end up on the floor. A few of my Male Avics were on the ground towards the end. Had to pre kill all their food and force hydrate them.
It sounds as though he may be coming towards the end of his days, You will find his abdomen will shrink. Just make sure he has water available especially if he's not eating.
Try placing him in a shallow water dish with the abdomen out of it and the fangs in it with the dish tilted at a shallow angle. This is considered far more effective then the traditional ICU. If he's just dehydrated, you might get a lot of improvement. In any event, its worth a try in my opinion.
If you can get that done and keep him in the same enclosure, so much the better. It'll stress him out a lot less.