I actually have my kids for more than 50% of the time and I work full-time. I can work from home a few days a week, I can vpn into my work (laptop), my kids are both in school full-time now so it works out. Mind you I was also able to do this the last 2 years when my youngest was only in school for half days while my oldest was in school for full days. Maybe it depends on your job and what you do specifically.

Yes I was paying all the bills, since I have my kids more than 50%, I don't pay any support, heck for a period of time I had them for 80-90% of the time, I'm actually pushing back on my wife to have them 50% of the time so that I can have a break and enjoy my life more.

You are painting yourself in a corner when you say you don't see how a working father can do these things.

There are many working fathers & mothers that don't receive financial support at all (alimony or child support) and work full-time and take care of their kids the majority of the time.

You have what is known as a self-limiting belief.

What is it you do that requires 70+ hours per week?

If you work 5 days a week, you are working more than 12 hours per day to get 70+ hours per week. Seriously, why are you killing yourself over this job, how important could it be? Couldn't you get another job for less hours?