Please read up on how live tiles work before speculating on why yours aren't updating. First of all, there's a hard cap by the OS on how many live tiles can be update (15), which might be the reason why some don't get updated. Second of all, it's the responsibility of your third party web service to initiate the updates to the tiles, and there could be any number of reasons why the third party web service isn't sending the push notification to the Microsoft servers. The primary reason is usually a setting for the app that the user must assign in order to receive the updates.
The bottomline is that phone memory has NOTHING TO DO with live tiles. Microsoft designed the live tiles in a way for the expressed purpose of not consuming any memory.
If your phone is crashing or locking up, it's most likely due to an overheating issue.