Not just yes, but Hell Yes! OP's father-in-law can retire early on the paltry $175 bucks a month his daughter sends over? Surely that ought to be cause for celebration on this forum!
Mdlerth, I often agree with your POV, but in this case, I have to question why OP's FIL thinks he has the right to have his daughter support him just because she got married. We don't know a lot, like how old FIL is, did he have any savings at all, etc. Is it a cultural thing that parents in the Philippines quit working when their kids get married and expect to be totally financially supported by them for the rest of their lives? If such a thing had been spelled out before the marriage and agreed to by the OP without limitation, then he has not much cause for complaint now, but it sounds as though this wasn't discussed in enough detail.
What about the sister? She isn't working right now because of supposed health issues, but she hasn't done anything to get the needed surgery, despite receiving some money for it. Is she making it up, intending to use OP as her meal ticket, too?
For reasons I don't care to get into right now, I have a bias against otherwise able-bodied parents who treat their kids like meal tickets/retirement plans. Please note that I'm not talking about parents who are doing the best they can for themselves and just need some financial assistance. (Other relatives also included.)
Retiring early at any particular age shouldn't be considered the most important thing in this whole marriage. It comes across as though the wife's income was a major consideration in deciding to marry, to more readily achieve his FIRE goal. OP's complaints aren't limited to just the money she's sending back to her family, but all the money she's spending on things she posts about on Facebook. Is she contributing anything to their FIRE goal, or does she spend it as fast as she makes it? How long as this been going on? Would she restrain her spending in time after the newness of her new lifestyle wears off?
Inquiring minds want to know....