Welcome to LRH Justin,
Your rifle sounds like a real nice rig. Here's my opinion on your rig and your plan.
Your goals as I understand them are to be able to shoot elk up to 1000 yds and your required accuracy is to be able to hit a 6" 100% of the time.
On your choice of cal and cartridge, I would say it is marginal. A 7mm can get the job done but bigger is better. The STW is a good cartridge but marginal to deliver an effective killing payload to 1K. If you're set on the 7mm I highly recommend going to the RUM at least for 1K elk. And whatever cartridge, go with the 180 VLD for higher BC and more mass and energy on target. (I personaly dont like them at closer ranges). If you already had the STW, I would say get the most out of it. But since this is a planned build, I would recommend rethinking your plan.
Since you are using a brake, I would recommend a .30 cal at least and no less than a RUM chambering.
On your personal standard of accuracy... that's going to be tough, and I would be surprised if you get past 700-800 yds. 6 inches @ 1000 yds is .55 MOA
and .5 MOA groups @ 1000 yds are rare, let alone .5 MOA accuracy which is different than shooting groups. And to expect it 100%.... welll, I just dont think you are going to get there. My standard for elk would be 18" @ 1000 yds. That is well within the kill zone.
Next, for precise accuracy @ 1K I would recomend another scope. You may have read some threads on it and if you have you will see that a BDC turret has limitations and the farther you try to reach with it, the greater it's limitations. Again, you have set a very high standard of accuracy and you will need as much precision as possible to get near it. A BDC turret is not a precise tool. It's a tool that sacrifices precision for simplicity. They can be useful, but they are a fudge tool and the more changes and distance you have, the more fudging you will have to do. Their clicks are 1/3 MOA, half of your stated accuracy requirement. In shooting extreme distances you will already have great challanges such as judging windage to name just one. If you mis-judge the wind by 1/2 mph and everything else about your shot is absolutley pefect, you have missed your 6" target by 2-3".
For 600-800 yd shooting where you dont encounter many changes, (elevation, temp, pressure, angle, etc) and you have an accurate rifle, you can probably at least come close to your 6" requirement with a Huskemaw.
You asked for an opinion and there it is. Can you kill elk @ 1K with a 7mm STW? I think so, but you will be stretching the limits. I dont believe you will attain your accuracy standard, especially with a non-precision scope.
Good shooting and hunting and keep us posted.