Re: Widget Bugs
First, you should not edit the core files–this includes the widget files. Instead, make copies of the widget files that you want to modify, give them a unique name, and then work on those copies. You can then install and activate your new widget in WPMU’s backend like any other widget.
Second, before modifying any widget, you should remove it from any BuddyPress theme column in which it is installed. This is just a wise precaution.
Third, I’d suggest copying back to their original locations, unaltered versions of the widget files that you modified.
Making a backup copy of your DB is always a good idea before any modification that can impact the data. But, as far as what you’ve done with your actual data in you DB, I cannot advise.