I loaded your map into the editor to see what the beef was with performance, and even on my relatively powerful machine the stuttering was pretty unbearable. The culprit is 100% those 340+ light objects, i bulk-deleted those from the hierarchy and like magic the stuttering was fixed. Unfortunately, light objects are rather taxing, and i can't recommend using any more than like 20 or so of them in a map, even the Vanilla maps try to use as few of them as possible.

the remaining 6000+ objects are a bit much for weak computers, but are otherwise not a problem for beefier ones. There are still some areas i glimpsed where you could benefit from some clever object reduction (like halving the skyscraper window numbers by using one long cube in the place of two smaller ones on opposite walls), but in total it's really not so bad without the lights.

Lastly, i haven't yet played this map properly, but i did see some suspicious spawn point locations. I did a guide on spawnpoints, maybe you can find inspiration from it. https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3004200610
Though EA 28 is bringing some updates to the spawn system, so this guide is going to be made slightly outdated very soon, especially when it comes to example #2. Hope it helps.