As to deleting the photos in the photos app two suggestions I can offer:
1. Choose Albums - moments - you will be able to select all the images for a particular day
2. In the Photos app - click on Select on right upper corner - then run your finger tip across a row and then down once you reach the right margin - once you reach the lower margin the app will automatically scroll and you won't have to raise your finger tip
Select as many as you want and then hit the trash can icon
Tip: Instead of stopping for the images you do not want deleted, come back to them after selecting a chunk - it goes faster that way