I know you said not to, but these are lots cheaper than buying the wrong parts.
ACTRON FUEL TESTER PRESSURE KIT CP7818 NEW SEALED | eBay
I bought one, works fine.
A leaky injector usually only drips when you shut it off. that's not going to be enough to hurt the cat.
it it was a major leak, you'd have driveability issues.
The pump - you can get them at the cheap stores that sell Chinese knock-offs. You'll have the opportunity to replace it in about a year or so. Get one from NAPA or the dealer - more expensive but last much longer.
The cats - the small ones near the engine are just screens (you can see right through them) - when you take the entire assembly apart you may find the screens are OK, just plugged. Remove the carbon with lacquer thinner and re-use. Soak it, brush what you can reach, blow it out with air. (Lacquer thinner will dissolve carbon slowly.)
The big Cat - call around to independent
muffler shops - not chain stores. They have OEM direct replacement Cats at nice prices. Or call smog shops - they usually know where the deals on Cats are.
Chain stores like Midas, Advance etc are way overpriced.