I think some people miss the point
Yeah. You got a mirror handy?
Lets have a look at what you said in your first post, (emphasis added)
I'm the kind of person that appreciates a challenge and therefore I've come to be my own worst critic. I've always strived for success and pushed myslef to extremes to master a variety of skills. As the years have passed, my passion for shooting for fun has grown into what some people have referred to as a 'sickness' in terms of striving for perfection when I'm shooting.
While my friends simply like to go out and shoot whatever targets we could come up with, I've always been the one trying to take it to the next level; setting up a variety of complex shots that require fine tuned shooting techniques in order to make the shot.
At any rate, I'm looking to expand my horizon, and would like to reach out to greater distance with larger calibers and really take my skill to another level.
If you really want to "master" long range shooting, and "take your skill to the next level", the gear you have is not going to hold you back.
True or false, connecting with a target at 1000-1500 yards will be just as easy with my .308 setup as it would with say a 338 or 50 or anything else for that matter?
False, of course. Do you want to learn to be a good shot, or do you want easier?
At 1000 yards, using the same missed wind call I mentioned above, You call the wind 60º at 8mph, it is really 90º at 12 mph. I am using my LR Rig, compared to what is possible with yours, a monster .30 Magnum, and a .50 BMG
.308 Win, 190 SMK @ 2500 FPS your wind will be off by 4.8 MOA or 50 inches.
6.5-06 140 SMK @ 2900 FPS, your wind will be off by 3.9 MOA, or 40 inches.
.30-378 WbyMag, 240gr SMK @ 2900 FPS your wind will be off by 2.6 MOA, or 27 inches.
50 BMG, 750 AMAX @ 2600 FPS, your wind will be off by 1.7 MOA, or 18 inches.
So yes, when you screw up the wind call, you won't be as far off target with the better LR rounds, but at the expense of punishing recoil, short barrel life, and fully 2X the powder charge for the .30-378 or 5X for the .50 (not to mention $2 per bullet).
When you get the wind right though, the result is the same if you are using a .308 or a 50 BMG, a hit. A .308 is just fine for 1000 yards, and capable of farther.
And frankly, if you can't shoot your rifle at 800 yards, it isn't the fault of the rifle. Hell, I shot a match to 800 yards with a Mosin Nagant with surplus military ammo and did tolerably well. My buddy shot the same match with a K98k and surplus ammo, the first time he had fired a rifle since he left the Army in the early 1990s and he did just fine as well.
It isn't quite clear from your posts, what sort of LR shooting are you planning on doing? Target shooting (for score) shooting groups, just ringing steel? What is your goal?