I'll give this one a shot; I've been working for banks or credit unions as a mortgage lender the past 10 years so I work with ratios and the types of things you are pondering on a daily basis
The answers to your questions are yes, and yes.
Back twenty years ago, when underwriting guidelines were more strict ragarding the debt to income ratios you are pondering.........the suggested total housing to income ratio was 28 percent and the total debt to income ratio was 36 percent. But that was BEFORE things were deducted out of your paystub. By using take home pay....as one should.....you are taking a much more conservative approach than most guidelines.
Today, lending guidelines will allow the total debt to income ratios....BEFORE anything is netted off that paystub, to go to 45 percent. With that being said, the people that are at that area struggle...aka....stress out week to week....paycheck to paycheck.
Regarding insurance, I'm a fan of term life . The amount you get it up to you, but if your intention is to have several kids it would be good to get more. I regret not insuring myself for more when I was young and it was cheap. I do have my retirement plans fairly well built up and when I was younger I looked at insurance as a waste of money since I was going to grow old and have a ton of investements. Not having three kids...well...I just hope I grow old so my strategey works. If you are having three kids....my bias....if it's cheap enough...is to go toward the higher end of your debate