So, I downloaded a mod where you have to go into the Thalmor Embassy, to start a war, so I play the mod, I enter before the actual questline for The Blades, the mod doesn't work, so I remove it, then everyone is acting as if they are in the party, with the blades quest, which is really annoying, is there a way to finish the quests, or to fix this?
Many mods save variables and strings in the save file, and if you remove the mod these orphans in your save file can make your game unstable.
The best fix to the game being buggy after removing a mod is to go back to a save from before the mod was added.
(Also, unless the mod has >1000 upvotes on Nexus Mods, I'd recommend testing future mod locations and content using console commands if necessary before committing to using them permanently)
The console command
player.setstage <quest id> <quest stage> is very useful with buggy quests, although I do suggest you save before you you attempt this, as sometimes, especially with main quests, certain conditions are required with certain stages. This also works if you want to just enter the quest without having actually started it, although as I said before, certain triggers are required and may break. The quest ID in this case (Diplomatic Immunity) is
As for the stage in this quest, it really depends on where you are in the quest and what quests you have done before. Going to stage
250 completely skips the quest, moving onto the next in the main questline, however it does skip all the previous main quests. Further quest options are below, but spoiler warning.
230will get you to talk to Delphine after whole the affair and acquiring the information, requiring you to go to Whiterun.
210is again after most of the quest, and you need to escape out of a trapdoor near the end of the embassy.
140skips the distraction portion of the party and gets you to continue exploring the embassy and fetch your gear.
Even more quest stages are accessible at the UESP site for the quest (spoiler warning) which I suggest you look at if you encounter any further problems in your game, or just browse in general. If you do skip the quest and wish to get out of the embassy quickly, use
coc whiterunorigin to quickly teleport to Whiterun, or replace
whiterun with any hold capital within wall's name to get there.