Hi Alison;

Assuming your valve is one of these 2:

Vari-Flow # I_VBVARI on right; Vari-Flo Control Valve Assy # SP07122 on left

it's very likely whatever fitting your backwash hose is clamped onto is a threaded fitting that can be unscrewed and replaced. It may be something like this:

(the photo links to the Amazon page, if the Hayward SPX1091Z4 Hose Adapter Replacement fitting is what you need.)

2. Regarding your vacuum, yes, suction can be much greater with the filter on waste, particularly if you've closed the valve to the main drain. In fact, with a SuperPump (which has greater 'suction' than most pool pumps), the port on the bottom of the skimmer can literally suck the 'meat' of your hand, if you cover it, and have the main drain valve closed!