Is Safecracker required for the EE forum to function and for users to edit their profiles, upload pictures etc.? My site is getting slow to load and one of the developers is suggesting that SafeCracker is one of the modules causing the issue. I don’t see the option to disable it but there is an option to uninstall it. Can I safely uninstall it?

No, Safecracker is not required for forums or user profile editing.  Safecracker is the EE2 way of handling user-contributed entries on the front end of your site.  Forum posting and profile editing, assuming you are using their native functionalities and not add-ons that change your member profiles to EE entries, have their own native editing routines (that admittedly don’t have the ability to be customized a great deal without a lot of work).