[determined]

I have worked on some nasty, rusty, dirty ugly looking ones over the years and have not broke a tab off yet.

If your pump is toast you are not going anywhere anyhow so clean it up and try removing it, you may be surprised.

Blow all the dirt off then scrub the area off with a brush and water as solvent does not do much to remove dirt.

Blow off the water then give it a good soaking with your favorite lube.

Personally I use a hammer with a 10 inch long brass drift.

Work your way around until things break free and you are good to go.