[@Master Crim]No if he has full control of his own mind then trying to tamper with it would simply end in him attempting to override said control by 'substituting it with his own reality'. If someone tried to convince him he couldn't walk on water then he'd turn the water to ice. When he's fully aware of someone is messing with him, since he knows a lot of tricks in the book and he himself knows what's 'normal' and what's not he can fight people who try to mess with him. His weakness lies not in the strength of his power but the which he is allowed to alter the area around him. He can effect the environment and change it to his whim.

I'll try and give an example:

An enemy magician has tried to make him climb down from the ledge thinking she has fooled him into thinking the floor is made up of lava. He looked down and chuckles. He just makes his feet cool enough that the lava hardens beneath it. Or he makes a glass floor protecting him from the danger. Likewise someone trying to read his mind would just find a miss match of bizarre memories and mismatched crap from old cartoons because his mind, as a result of his powers, has become really hard to decipher. It's not so much that he's actively blocking it as his mind is just so full of unquestionably nonsensical things that it's really really hard to alter or change. Reality warping is an extremely dangerous power and very potent at that. However he is no mad jim jaspers. He can't make his own dimensions nor can he destroy them. He can change things in the physical world, or otherwise into whatever nonsense he wants. He can turn a cane into a snake. But he can't make independently thinking life, nor can he make dimensions so much as he can pull whatever he wants out of his hat. However if you shoot him full of some sort of drug that either hinders his ability to think, or focus then that puts him at a big disadvantage. Because he can't focus properly enough to use his powers. Likewise if you surprise him and not the otherway around and someone manage to corner him that way or get him before he notices he can't exactly fight back he doesn't can't see 360 degrees around him. His perceptiveness is that of a normal person.