Basically, the game crashes whenever I fast travel probably due to mods corrupting game files (which perfectly works fine yesterday, hence, I overwritten the save files.) As a last resort, I tried to load an old save file, but it crashed upon loading. So it seems I have to restart the whole game again.

So Im wondering if there is a way to automatically complete quests. (As in getting rewards and not having to clear dungeons and NPC interactions). Also, I cant just unlock shouts via console and spending dragon souls. I have to completely go through entire quests and into dragon walls to get them. Is there an alternate way to get them?

Perhaps you could try updating quest status using the consul, to automatically complete them. Beyond that I'm not sure.