I was a software engineer from 1991 to 2004. Then I quit, sold my house, and am now living off my retirement savings while I take premed courses. I'm living like I did when I was 19, I feel like I'm 27, and I just turned 40. No husband, no kids, no mortgage, so it's quite a comfortable lifestyle. I'll be just about broke when I start med school, and I'll have big scary loans to pay off when I'm done with residency around age 50.
Money isn't the reason I want to be a doctor, not at all. Why would I spend 10 years training to switch from one 6 figure job to another? Money is also not going to keep me from being a doctor, see above re: going for broke.
If you want to be a doctor, go for it. If you're not sure, volunteer someplace and get a feel for it. There's nothing foolish about leaving a high-paying job to pursue a career that fits you: you'll live longer, and you'll have more to give.
What's with the getting fired and not being employable in old age bit? Getting laid off is not getting fired. In software and everywhere it's always a pain in the ass to get your resume together, put on a suit and play the interview game. But if your resume is at all interesting, you will always have a software engineering job. There's too much code out there that needs maintainance, support and improvement for jobs to evaporate. You might need to relocate to Seattle or the Bay Area, and you might not get rich on options, but not being able to find a software job is a strange thing to worry about, imho.
I have two suggestions for you.
1. For me, keeping one foot in software for the income, and one foot in school for premed, was not sustainable at all. Think about quitting your job for 2 years to be in school full time (plus MCAT, volunteering and/or research), and then you have a "glide year" to make money as a contractor while you interview for med school. Doing this feels very serious and responsible to me.
2. No offense, please don't take offense, but may I say your English is not strong. For better or worse, a strong ability to communicate in verbal and written English is an absolute requirement in med school admissions. I suggest that you take English writing classes (some med schools require 2 years of English composition anyway) and look for volunteer or work opportunities with a ton of public contact. And whatever your first language is, it's a HUGE asset to be bilingual, and if you grew up outside the US and are now a citizen, that's a personal statement asset as well.
Best of luck to you regardless.