I am a retired American Airlines pilot, so I DO know the industry.
First, as you already know, there is no guarantee that you won't be furloughed at least once from a main line carrier. The worst case, after 9/11, saw some pilots furloughed for a decade or more.
Unfortunately, as a new hire at a main line, you'd get the worst schedules, which normally equate to either sitting reserve and/or flying a lot, and mucho time away from home. That's the biz, sweetheart, and it sucks since you've got kids and want to spend time with them NOW, rather than when they're in high school.
Frankly, I am SHOCKED that a sim instructor can make 250k. But I also know that just like the pilot shortage, there's an instructor shortage. But as you also know, you can make a buttload more money as a line pilot than as a sim instructor. We're talking MILLIONS more over a 35 year career. So it's a major factor to be considered with your life.
Personally, I was never in the fly-to-live group. It was a satisfying career, but I don't miss it. I was a low time guy, trying to get the most money for the least time away from home. If you do that, especially as you gain seniority, life can be pretty nice. I don't think I'd like to be a sim instructor for ten or more years. Same material, same students. Nothing new and exciting, unless you love changes to approach procedures. Flying, meanwhile, lets you vary your destinations, aircraft, layovers, etc. Always something different (not to mention the challenges you face on a daily basis just operation from point A to point B. Extremely satisfying to get an aircraft safely to a destination with horrible winds and weather.
As a late retiree, I can't speak to retiring in your 40s. If you want to do it from your current job, AND YOUR WIFE IS TOTALLY ON BOARD, great. I'd just hate to be in a position of "Let's wait until the kids graduate from college/law school/med school, etc., or never feeling comfortable with the nest egg you've built up, so you keep working a drudge job.
Remember, seniority is EVERYTHING, so if you're going to jump, DO IT NOW! Especially if you're planning to have another child, get the crappy away from home years behind you. Pick an airline that has the bases that you find appealing. I'd avoid American- they have the worst employee relationships, and are ALWAYS behind the other main line on wages and quality of life. BUT, if you need to be based in a certain city, even AA isn't a horrible way to go. I'd go with Delta, Southwest, Alaska, or United, in that order.
Good luck!