Josh,
Regarding the washer issue: I think the bolt selection was based on the overall length requirements on bare metal. The powder coating is pretty thick and adding that dimension to the overall distance can challenge the bolt that is included with the kit. From time to time, I would order one step longer bolts from ACS. I always had trouble ordering just one and it resulted in a nice selection of various length bolts in the common diameters. I would suggest getting longer bolts. Then too, I would order washers in hundreds 2-3 cents apiece and nuts in lots of 25s so I always had a fresh nut if I had to remove one more than a couple of times. Over time, I also accumulated a collection of pull rivets, solid rivets, clecos, etc.

The reamed hole issue is because the tab has much less bearing surface and to prevent wear there, the bolt should fit tightly to prevent rotation. I suspect you can accomplish the same goal, by putting a drop of high strength Loctite under the bolt head, If you grease the bell crank rather than the bolt when assembling there shouldn't be grease between the bolt head and the tab.
Lowell