Ray is correct, you should not be able to remove the suction side nipple from the pump housing.I could be mistaken, but I believe that hose nipple was originally a press-fit into the pump housing (no O-ring used or needed). To seal it up and keep it from pulling back out, you'll probably need to use some sort of sealer / adhesive ... something like a sleeve retaining compound would probably work good.
No, it's to thick and it's brittle when cured. Use a Loctite retaing compound like 620 if you have up to .005 clearance or use 680 up to .015. Clean, follow instructions and allow to cure fully (24 hours at 75F or above!Would JB weld work to bond that nipple in place?