Question: Should I stay in my current role, ask for a pay rise, or find somewhere new?

Situation:
Right now, I'm effectively doing a lead developer role for half the salary of the other member of my team- I'm code reviewing their work (which often has many many errors in it), creating and assigning tickets for both myself and them and engaging in many meetings with senior staff in the company. The other dev in my team has more experience on paper, but the amount of work they are generating is approximately 1/5th of what I produce. I'm really disappointed that when I raised this with my manager & then HR, they have seeming done nothing about the situation. It's really disheartening and it feels as though I'm not really valued.

I don't really have much loyalty to the company, but because I have helped build their internal system from scratch I'd loathe to leave it in the incompetent hands of my colleague (who at present still has a month left of probation).

I can give any further info if you'd like it but I could really do with some advice right now.

Woo, rant time.

I've recently changed jobs to a new company due to a number of factors at my old job. I didn't tell my old boss (let's call him X) my expected salary, nor did I tell him which company I was going to.

However, I've been informed by someone that still works there that X has been discussing my new wage in front of everyone; he was telling everyone that I'm going to lose money by moving job and that I made a stupid decision.
I didn't leave due to money, it was due to X's inability to take constructive criticism, the constant subtle sexism of the office and just a generally bad overall feeling about the job/office going forward. Yes, I will admit that money did have a minor part in my decision to leave but I didn't verbalise that to anyone in the office, and I made X aware that my departure wasn't to do with money. I left on good terms.

I feel as though it was wrong of X to talk about his opinions on my new job in front of my ex-colleagues and friends. I don't know, maybe this is the norm and I've just been living in a cave before this, or maybe my last boss was just a bit of a douchenugget. Has anyone else had this experience?

I've got to meet up with everyone from my last place tomorrow to properly say goodbye and things.. but I'm not sure how to approach my old boss when leaving drinks are held now. Should I say anything? Should I just act as though I know nothing about it?

What would you guys do in this situation???