I couldn't undo the connector on the bigger hard line coming off my old fuel pump. I cut it because I thought it would make it easier to wrench on, but still no luck. I've had it soak for two nights with PB Blaster, still cant get it too budge, and now the smaller nut is rounding off.

See my predicament here!

How would I go about cutting/replacing this?

The new fuel pump has the male end.

 

Wow that sure looks familiar .

Maybe time to invest in some line wrenches .

Do you know how to flare double flares and have a flaring tool ??

You can make your own fuel pressure line out of the copper/ nickle line.

see if the new line is still able to bought from the dealer.

Use fuel injection line and the proper clamps although going to different inner diameters you might need a adapter barbed fitting .

 

Definitely use line wrenches (aka flare nut wrench) when working on fuel lines and brake lines. For the stubborn ones I use my crows foot flare nut wrenches attached to a flex head.

If a socket is no longer fitting on the male end, try locking pliers. I would slip a box end wrench over the female end since the line has been cut. Use a good pair of locking pliers tightly fitted to the male and give it a turn.

If that doesn't work, that female end hose is about $20 from the dealer. Or at least it was the last time I bought one. I have one laying in my garage right now. Just make sure to use flare nut wrenches on the other end to avoid damage to the other end of the hard line.