Absolutely, I need to do what I think is right, I guess I'm asking for other opinions because I don't know if I'm the one being unreasonable, or if they are, and it's nice to get a few other perspectives.
I just spoke to a good friend at work here who I trust, and he said the same as you. They're treating me like a fool, and there is no way I should take it.
There is a little history - I'm an immigrant, they helped me get Permanent Residency, and I've always been underpaid. The company has a chronic history of underpaying and undervaluing tech people.
They need me, no doubt about it, but they're also letting a lot of very, very good people across the company walk out. Three friends in the last three months have stood their ground and eventually just walked out, the company didn't try to offer them anything to stay on, even though they're doing the work of 10 people and are basically irreplaceable.
I think I'll go for the polite yet firm "It's not reasonable to ask me to take on increased word, responsibilities AND be on call with any extra compensation at all. No thanks".