My question is, how much water shall I bring? When hiking in Colorado, my water consumption is typically one litre every 5 miles and 1,500' gain. For example, two litres for a ten mile, 3k feet gain round trip. I should be able to pump water at one of those lakes along the MR, right? My plan is to take 2 litres and the filter with me, refill at UBSL, summit, and then refill again at switchback #23. Does it sound reasonable or too risky?
Within a mile, you have water at the split between the main trail and the North Fork. You'll pass water twice before reaching the Ebersbacher Ledges. You'll have another water source before Lower Boyscout Lake. You can refill a Clyde's Meadow before reaching Upper Boyscout Lake. There is another Lake (I believe it's call the Frog Pond) and a waterfall before Iceberg Lake. From the trail head to Iceberg Lake is probably 4-5 miles tops. You will not have anything after that though. What I'm trying to say is that you have plenty of water sources all along the route. Personally, I drink a liter at the trail head and hydrate at the various water sources I listed. I don't carry any in my pack. You can if you want to play it safe.
Do people do running belays on MR? What's the "sketchiness" of this route compared to the east ridge of Mt. Russell?
I think Russell is a much greater "sketchiness" factor than the MR. If you feel comfortable on the East Ridge, the MR will feel like a walk in the park.