So, I did a lot of experimenting on my own, and I fixed the majority of it. (Minor things missing.)
After relaunching the game with the new addons removed - (Bricks and that one weapon addon) - and noticing no changes, I loaded the modified save once again. (The save where I took out the line that the original save had an error with.) This time, once I loaded the modified save and received another error, I noticed that the error was slightly different.
The original error had a 0 and the new one had a 2. After realizing this, I turned the modified save (I'll refer to the this one and the ones after as Modified Save 1, 2, 3) back into a text file, opened notepad, and deleted the line once again. Dubbing this new save Modified Save 2, I load it in Blockland once again. I get another error once more, but also a large portion of the missing blocks are now loaded. Clearly I was on my way to restoring the full save this route.
(By the way, I noticed that between the first and second errors, a small amount of bricks had returned. I didn't think much of it and that's why I didn't note it previously, thinking it was just some odd fluke.)
Well, I opened the text version of the file, deleted the error once more, and loaded the save.
Everything loaded completely with no errors!
At least; mostly everything.
3 button blocks were missing. I have a feeling those errors are related to those, so I didn't bother messing with it. Also, a large chunk of the map was missing too, but I have a feeling a player deleted this portion instead of it not loading correctly. Mostly since I didn't check this portion until the last save was loaded.
So there we have it! That's my experience with this mess-up. I don't need any more help per se but I'd like to know more about it.
P.S. In case someone else runs into this problem, I notice the errors show up near the +-EVENT portion of the txt files. I don't know if this is the case all the time. Also the errors being with a naked quote, (" ) followed by a space then a string of numbers representing a block's positoning. That should help you find the errors in advance.
Anyways, thanks Goth77 for helping me out, and everyone else who had the problem in the past.