It might help the DLC issue by deleting the DLC and then redownloading it and see if it's fixed. I personally just didn't install the preorder DLC and haven't had any issues with corrupted saves.
Unfortunately that won't help at all, I have no pre-order DLC, I bought it in a shop couple of days after release and I still got the bug after one playthrough, people have mentioned various reasons for the bug; going into any of the vaults, when NPC's and critters fall through the ground on death, my current playthrough, avoiding vaults is at about 80 hours, with the only glitches being one quest and rocks that don't quite meet the ground, although I did have to read up on some things to avoid them, such as Raul's personal quest, yay for roleplaying via Fallout wiki........
The DLC bug is only related to DLC in that the bug causes the system to look for something that isn't there, which is coded as DLC.
As you never installed the pre-order DLC, may I ask did you accept the first, and so far only update?.