I had a run yesterday of 3250 meters and had no fps drop all along for the first time. I dont know if its your last patch that solved something or if a/multiple thing creating a leak has not spawned.
I did not encountered turrets, turret vehicles, big outpost. (which i suspect turret might not delete correctly)

For the freezing problem, you could first generate 2000x500 and in this section, a couple frames later, the npcs and at very last items. Spreading the load. Even then you could spread the generation over multiple frames.

Is it possible to implement a pooling system, where it loads the chunks in at the very start of the game and takes from the pool when the player advances forward. Only thing to be loaded would be enemies and loot I guess, even randomized buildings would be preloaded

Wanna let ya know that the performance has been significantly boosted off the last update.

My issue with the freezing/loading is that it seems to tend to happen when approaching an enemy position, and I wouldn't mind it happening normally but when I'm trying to aim my 30mm autocannon at a bunch of guys about to tear up my bmp, it's really annoying that it chooses that instant to start loading the next chunk.

Placement of enemy positions should be changed so that the loading happens shortly after clearing a position and moving to the next, as it is it gets very annoying trying to enjoy the actual meat of the gameplay in mors longa just for the game to decide now is perfect for loading 200m of road.