I'm in December and have managed to liberate 4 regions and kill one of the Chosen. However the game is getting pretty hard as FL is at 18, and I feel like I'm lagging behind in terms of technology and high-level soldiers. I got some coil guns, but about 2/3 of my guys still use laser guns. The enemy starts fielding troops with lots of HP and weapons that can cut through my Alloy platings like butter.

In hind sight I think I made 2 mistakes (among others):
1. I mostly did missions of the liberation and rescuing resistance personnel type, and skipped many intel/supply gathering missions. While this helps with keeping Advent's vigilance in check, I think I might have made my troops under-level and missed out on collecting corpses for research purpose.
2. I was overly reliant on DFA Sharpshooters and Trial by Fire. The result is that most of my high-level troops are Sharpshooters and Reapers (I have about 5-6 MGST, including 1 Shinobi and 1 Grenadier, while the rest are snipers), and the majority of my remaining soldiers are at SGT level, plus a few Squaddies.

I'm trying to see if I should reload an earlier saves (I saved every time I get a supply drop), or just power through. Would be great if anyone could tell me what I should do differently in the strategy layer.