Possible life changing decision on the horizon

So I got a phone call yesterday about a job I applied for a while back. This job I applied for thinking I wouldn't even get noticed, but you never know. We I did get noticed and they wanted to do a phone interview.
This position is the job I've set as my goal since the day I graduated high school, it's what I went to college 3 times for and continued working to gain 15 years experience for. It's a career move to a position and company I could possibly retire from.

The company is HUGE in the healthcare industry. Pay, benefits, perks, and everything else that goes along with it is life changing for me. The salary alone will almost double what I'm making now with tons of room for growth.

They called me yesterday asking me to get back with them about it. I called back when I was free and spoke with the hiring manager for about 45 minutes and it went great. He told me he's looking to hire between 8 and 10 people and has narrowed down 30 resumes, so that's pretty good odds already.
At the end of the call, he told me he was impressed and wanted me to come in for a face to face interview. He pointed out that I easily made it through the first round. Great!!!

Now the bad. The job is in Houston, I live in Austin and I'm well rooted here. My fiance has no issues with moving to Houston. Her job requires that she live in the major metro in Texas, so she's pretty free in that sense. However, I have joint custody of my kid and this would require me to move 3 hours away from him.
As it is now, I have him between 60-70% of the time. This wouldn't be possible if this plays out and I move. I would be limited to every other weekend, holidays, and some extended time during summer, maybe even the entire summer. He's 7 and we are very close. My dad wasn't there for me as a child and I don't want to do the same to him. I know I shouldn't be, but I'm already stressing about this and it's not even a sure thing at this point.

If I am offered the position, I'll have regrets either way. If I pass on the offer, it's likely I'll never be presented with an opportunity like this again. If I accept, I lose significant time with my kid and force a change in his life. Ideally, I'd like to have full custody and take him with me but that will never happen. It's not like his mom is a bad parent, so it's pointless to try and fight for custody.


Any of you ever faced a decision like this? How did you handle it?