“The gazelle” you remind me a bit of me when I was younger. I grew up extremely slender. We’re talking 5’11” and 110 lbs. I had some bad experiences with recoil as a kid and it haunted me. I can tell you’re quite fearful and I have memories of being the same way.
As an older man, now about 180lbs I don’t mind recoil at all. From my experience, neither recoil nor noise is heard when you have a big game animal in your sights.
At the range, I’m comfortable shooting 30’06, 270, 7mm-08 as much as I please. In fact, I owned a vanguard in 300wm for a while which I found tolerable from the bench.
So what changed for me? Was it just my mass? No. It was 99% mental with 1% technique. The way you’ve described your fear of what a 45-70 would do to you, and your dread at anticipating the shot tells me you need to work on that 99%. When I hear someone complain about the scope touching their face, I know there’s a major fundamental problem.
Really, if you do figure out that 1%, it will make the 99% easier.
The rifle won’t hurt you. People who talk about sore shoulders aren’t shooting correctly. The butt of the rifle should reside between the clavical and the shoulder. Feel the soft pocket between. That’s the spot! If you feel it on the shoulder, you’re holding it wrong. You want the rifle to be pulled into the pocket firmly so that it doesn’t have a chance to run up on you. You want it to push you, not punch you. Although you’re holding the rifle firmly against you, be relaxed and free to move. When the rifle moves backwards, your upper body should move freely with it. That’s key. Lastly, RELAX. It’s fun and it won’t hurt you. If the rifle is already pulled into the pocket and your body is free to rock backwards with the recoil, the scope can never hurt you.
I would suggest avoiding the bench for a while. Shoot from standing, leaning your upper body forward into the rifle so that as it recoils your torso rocks back into an upright position rather than leaning backwards. Get some practice sitting with one knee up and your forward elbow on that knee supporting the fore stock. Again, don’t be afraid of the rifle but rather lean into it. Hold it firmly into that pocket and stay relaxed and loose.
Keep your cheek pressed firmly (yet relaxed) against the buttstock. Again, you’re looking for a push not a punch. Keep your mouth closed and make sure your teeth aren’t apart.
Consider some reduced recoil loads.
Consider using a PAST recoil pad. I own one though it doesn’t see use anymore. It had its purpose for me at one time.
Layer up! When I’m hunting in late fall im northern Alberta you can believe I’ll be wearing layers. So guess how I practice? In a t-shirt? Nope. Layers and a jacket. It helps a lot, actually.
Consider a heavier rifle. A weatherby vanguard with a 24”bbl has less felt recoil than a tikka.
Please consider trying some of these techniques. They all fall under the 1% category but if you can get that sorted out, the 99% mental issue will come along nicely once you realize you’re shooting and having fun without being hurt. You will soon forget about recoil.
If you do practice from these common field positions (recommend against prone for now) you will likely find that you’re a far better rifleman than most. There are no benches in the field.
Maybe my advice is worth what you pay for it, but in this case I think you may find it helpful.