The website sounds good and the testimonials sound good and the pictures make him look good.
And maybe he's the real deal. Maybe he's so good that he can make the 2 week claims. You never know...
That said, I'd want to be there at least the first week, every day to see how he gets from ground to saddle in that first week like he says he can do with ease.
Maybe he's the quiet calm type that can get the job done and that would be great. There are a lot of trainers who have a natural knack who can get further faster with horses than others. Anything is possible.
I think I'd follow the advice you've been given here,...check up personally through phone or better yet, in person with the past and present horses he'd trained or has in training.
If you like what you see and hear and want to go for the 2 week deal, then be there every day at least for the first week to watch him in action with your horse. What does he do that first week? Does he lay the horse down? If so, how? (some "nh" trainers lay the horse down first and foremost)
If he's going to do anything good, bad or ugly, it'll more than likely be in that first week.