That scale looks good…..although if you are going that big you might want to get one slightly bigger that can weigh your entire pack as you're on the way out the door.
Regarding your concerns with handling extreme weather….this is not an issue that concerns me. From the BPL review:
"Although I was not able to test the tent in winds stronger than 20 miles per hour, I at least found that the Carbon Reflex 2 is stable in moderate winds. The tent is basically a dome shape which helps it shed wind."
"we were frankly quite surprised and impressed with the tent's storm and condensation resistance."
"The MSR Carbon Reflex will handle a coating of snow"
Overall, I think the tent is a sturdy enough for a 3 season unit. I think it can handle pretty stiff winds and it would shed snow pretty well.
I do not think the carbon fibre poles are going to be what fails (if something does). I think the poles are quite strong and if they were to break it would likely because of a sharp focused impact force (which cracks the carbon) like stepping on the pole.
If something were to fail, I think the first thing to go would be the poles tearing out of the dirt in extreme winds. If you had poor soil and extreme winds this might be a concern. If you were on sandy soil you might want to tie it off instead.
Besides that, I think a heavy snow load (ie. +6") could take the tent down, but that's not this tents intended purpose and besides, you likely wouldn't accumulate this much snow because the tents shape would shed it well. You'd probably need to get a foot of snow on the ground to get 6" on the tent. I'm just speculating here.
If you are going to ditch the CR2 for a different tent, I would say the two best reasons are:
1) You want something roomier
2) You want something lighter
A single wall tent will generally be roomier (because they need to be so you don't get covered in condensation). If you went with a single wall, you'd save about 1/2lbs and get a roomier tent, but you'd have the condensation and misting issues, plus you'd have less versatility if you want to use a fly/footprint/poles setup or if you want to use it without the fly to see the stars etc. I like how with a double wall you can leave the doors open in the evening and sit inside the bug free area with a nice view still.
If you went with a double wall, you'd be buying a roomier one that would also weigh more….probably at least 1/2lbs more for a roomier 2 person.
So really it's a 1/2lbs heavier but roomier double wall or a 1/2 lbs lighter and roomier single wall. A double wall that is a roomy as the double rainbow will probably be a full pound heavier than the DR.
I would decide on the single wall vs. double wall issue first. If you are okay with going single wall then you've got some nice options. If you don't want to go single wall, then it's a question of weather you want to add weight for a bit more space.