I carried the real SDM-R during my latest tour in the Middle East.
Some comments for you:
You're probably going to want to use a free-floated rail system. The point of the SDM-R is to provide accurate fire out to 500-800m, even while using accessories mounted to the handguard and a bipod. The DD 12.0 SDM rail system is the real thing, but it's a bit expensive. There are plenty of cheap free floats, the cheapest one that you might want to use being the YHM rifle-length free float.
Basically, if you don't at least free float, I wouldn't go so far as to call your rifle anything like an SDM-R.
The SDM-R's barrel has 12 flutes and uses an FSB attached by set-screws rather than the traditional taper pins.
BUIS-wise, if you want to be more accurate as far as the real thing goes, use the Matech 600m BUIS. You can often find them in the EE here for $70-$80.
LaRue throw lever mounts are the best. I won't go into detail, as there are a billion threads on them alread on the board
You don't need to raise the scope above the iron sight. That would place it too high anyway. It will see "around" the FSB, so don't worry about it. You want the ocular at the same height irons would be anyway so you can use a consistent cheek weld.
For a cheaper alternative to the ACOG on your SDM-R, I recommend either the IOR 3x25 QRTS or the IOR 4x24 M2. That second one has spectacular glass, a great reticle, and will run you about $350.