Dry mouth is a side effect (although an uncommon one) of both the medications you're taking. It may help to take them at a different time of day if that's allowed (check with pharmacist). If it's really severe or debilitating see your GP as he could prescribe an alternative. DH takes BP meds and has had to juggle timings and change the medications until he found the right combinations/timing to lessen the side effects.
Probably means that you are breathing through your mouth during the night. Perhaps a chin strap to prevent you from opening your mouth might help. Amazon does sell some tablets which help a dry mouth at nights.
As above. I wake up every morning with this and it is quite uncomfortable. I am on Irbesartan and lercandipine for high BP. I also have an overactive bladder so wake at night with both conditions? Any ideas?