You say you've tried pads, grass, etc. and that you've let him out; but otherwise what efforts have you personally made in supervising him?? The key to potty training isn't just to offer him a place to go; but to supervise and watch him like a hawk until he is reliable. If you've exhausted all other efforts, I would advice trying Tether Training; where you hook up a leash to him on a harness and the other end of the leash to your belt loop. So this basically ensures he is with YOU at all times, while you're doing dishes, watching tv, whatever. He cannot be allowed to have the privilege of any freedom until he has caught on; that's the biggest mistake most people make. They think if they just leave a pad or litter box accessible that the dog will know to use it; and that's not the case. He needs to be with you at all times; or at least where you can watch him. The key is to PREVENT every accident from happening. Once he begins to potty; immediately pick him up and redirect him to the proper location. If you weren't paying attention and he already went, that's the owners fault for not watching him and too late to do anything. It DOES take a lot of diligence in the beginning; but they catch on very quickly this way when you're basically only allowing them to potty in one place. And as you already are doing; take him to his potty area (outside or wherever) frequently, and if he DOES go, praise tons!!! The key truly is to keep constant supervision. Sometimes though, that isn't realistic (like when you go to work, or leave the house to run errands, or at night) and during those times he should be kept in a pen. Make sure to clearly distinguish one side as his bed with toys, chewies, blankets, etc. and the OTHER side just for a potty pad or patch. (See pic below, this is how ours looks.)

The dogs natural aversion to soiling it's own bed will cause it to use the opposite side when it has to go potty. It also reinforces the substrate preference to use whatever medium you chose; so that as long as the same thing is available otherwise he should eventually learn to seek it out.
Also, since he has to remain intact if he is also MARKING (instead of just relieving himself) investing in a belly band will be your best bet! They are just pieces of fabric with velcro on one side; you put a feminine pad in the inside to absorb and it wraps around the dogs belly & penis. So when he lifts his leg to mark, it doesn't get on your furniture or whatever. =)
Welcome to the forum, take a look around and you'll find lots more tips and suggestions. Oh and we loooove pictures here.