How to handle enemies on the high level in Fallout 4?

I'm playing on my save for a while and I reached high level. I'm playing a stealth-VATS build and got all sneaky perks I needed to deal big damage with sneak attacks. But lately the enemies are getting so tough with how much HP they got that I hardly kill an enemy with a single sneak attack, not counting obviously super weak enemies. Okay, my Gauss Rifle is still one-shooting most enemies with sneak critical hit, but I can't use it on every single enemy, that rare ammo will go dry quick.

So I did reach the peak of my sneak build, and now I'm honestly start to be afraid of every level up, as it makes my weapons bit by bit weaker compared to enemies that slowly turn into a bullet sponges. So, what do I do? Sneak attacks start to stop paying off. I have a Power Armor (Hellfire Mk VI looted from some enemy) ready for direct combat, but I would need to spend a lot of perk points to be able to actually handle a direct combat.

TL;DR High-level enemies got tons of health and my sneak build is not keeping up. What should I do to be back in the saddle?