Uneven copper bellow threading when replacing copper pipes with PEX
Maybe you can use a hand file or a sharpening stone to get a surface flat enough for the ring washer to seal on, hand-held power tools are unlikely to produce a satisfactory result. But your best bet is probably teflon thread sealing tape. it takes crazy amounts of tape to get a good seal. put 6 or 7 layers on 

That hose clamp looks kind of dodgy, I think those connectors are intended for use with crimp rings, you should probably use a connector system that you have the correct tools for, EG one of the push-on or screw compression types,