Ole Yeller...
Here's what I got. The stock wheels are a 50mm offset, as you said. The Mazda Millenia wheels are 15x6 w/ a 50mm offset (I was wrong before). The 50mm was stamped and verified.

The 225's on the Mazda wheels w/o spacers, will rub both on the inner front wheel well (near the trans housing) and on the rear trailing arm. This comes from the previous owner, whom I trust.

With the 5mm spacers in place, I'm creating a 15x6 w/ 45mm offset, which works w/o rubbing.

Regarding the 7-inch width you're looking at, I think it's fine since you're adding 1/2-inch to each side of the wheel, but not affecting the 225 width which is more than the wheel.
The 225's w/ 5mm spacers stand proud of the side of the car, just a little bit. They look good and 'strong'. For this reason, I would not recommend the 38mm offset, which, as you said, add's a lot to outside dimension.

If you do decide to buy, and test fit them as Descartesfool suggested, here's what I'd do. Measure the distance from the hub center to the fender lip. Jack the car and remove the strut. With the car still in the air, mount the wheel/tire, and jack it up into position using your measured ride height. This will allow you to look all around for clearance with the car in the air and the wheel/tire in the correct position. If you leave the strut on, you won't be able to lift your suspension high enough (the suspension will compress some and then lift the car off the stands).

I wasn't able to run the race tires during the autocross, yes it really was that wet, but I really love the new R. I got the fitment info from a test fit I did on Saturday. I'll try to post pic's of the tires soon.

Sorry that I can't give you exactly what you're looking for, but I hope this helps.