I personoly don't think that the words "long range" and "light weight" should be allowed to be used in the same sentance!! Light weight is not what you should be striving for.
That being said, what do you consider light weight? I can't imagin that the combo you came up with would be considered "light weight" in most peoples opinion. I gotta figure you will be at least 12 LBS min on the road. I have never held an A3, but the A5 that we use is fairly heavy. I'm not sure about how heavy the #4 and 5 tubes are ....all of my remmys are Rem Varment contour. Krieger says that the #5 contour is 1/2 pound lighter than the varment contour. I would think that this coubo would be great for 800 yard work.
The 11 or 10 twist will both work fine for the 210 Bergers, I have both in my 1K comp guns. If you are going to try go up in weight some day (as in the new 230 TAC Hybird from berger) I would go to 10 twist.
I have had great luck with RL22 in the 300 win. H1000 is also very good. Use Fed 215 primers.
Good luck, and have fun!!!!!