Well, there could be many causes for a particular problem. The best way is to isolate them one-by-one.
Regarding your rx_lev changes:
1.Have you checked the path balance of the cell ? It should be checkec per TRX wise.
2. Is that problem is on particular TRX or in the entire cell ?
3. Do let me know this, then may be I can suggest you some more solutions.
If it is cell specific problem, BSC level settings would hardly matter at times.
Regarding your 7743 & 7746 alarms:
1.In BSC settings you must have defined some threshold for this alarms, check whether is it a network wide problem or cell specific problem.
Revert incase of case of any clarifications if required.