That sucks, but I can see that happening. The first time I played my thumb got a bit stained, but after adjusting my grip it's been fine. Everybody's hands are different of course, so I don't know what would work for you.

The controls are okay, but it's very obviously a game designed for mouse and keyboard. I use the right track pad to control the pointer, and one thing I've found that makes it easier in building mode, is just moving the camera with the left stick instead of trying to move the pointer to draw a long wall for example.

Some things just remain annoying though, like scrolling through the endless list of wallpapers. There's just no way around moving the pointer all the way to the arrow to click to the next page and back again to select something. It is what it is. I just accept that it's a slower experience.