You are already incubating a start-up - it's your child.
Your sole task is to keep the cash register chiming bimonthly. Focus on the job that pays you, if you have extra time then work harder for your current employer. Pile up some good karma.
Run those errands, be with your spouse, speak much less than spoken to, & forget your buddies.
Also be on excellent terms with your in-laws.
I do have a dream to run my own startups, but I guess I'm "too old" for that now and I didn't see anyone in the age of 40+ founding their first startup in the valley.
I guess I'll have to give up my desire now
I haven't seen anything about what you will gain in your career from being an involved parent. You will gain perspective. You will want a better future for the world, for your own kid. That perspective can help you see things that others don't see in the tech industry.
Quick story: I am a teacher, and recently I've been inviting elders into my classroom to tell their life stories to students. I sit on the side of the room, and students drive the conversation. One question students have asked every elder: "What was the best day of your life?"
Every elder so far (n=3 and counting) has looked around at everyone in the room, smiled, and said with conviction, "The day my kid was born."
Congratulations, and enjoy this time in your life. :)
Maybe you just need more focus and better manage the time you have.
If you are a good engineer, then you will have a job. If not at your current employer, then somewhere else. Do the work for your employer at your job, not on your own time. This includes learning new things. You learn by doing, so if you need to evaluate X as a possibility of solving Y problem, then do it on the job. If it's not valuable enough for your employer to be paying you for this time, then why bother evaluating it? If X is something none of your devs know anything about, should you really be using it? Maybe there is something less sexy which already well serves that purpose. Maybe you should hire someone who knows X well. Or maybe hire a consultant. If you find yourself regularly having to devote more than a typical 40 hour work week to your job, then maybe that's a result of bad management from your employer. In this case, find a different job. Let the founders slave away at their business, it's their baby, not yours.
For your start-up ideas, maybe you need more focus. The Apple approach is to start with the customer experience with the product and work backwards to the technology. It sounds like you might be too wrapped up in the engineering side. Think of one thing that people will love or that will really help people and work backwards from there. Try selling the thing before you write a single line of code. Put aside a block of time every night when the child (and mother) is sleeping. You can probably accomplish a lot more with a heavy focus put into two hours of time than you can with little focus in a whole day. Repeat this every day and I bet you would be amazed at what you could accomplish.
The tech culture is great, but more important is probably the culture of the people you are trying to sell to. Find your customer and you find the culture you should be immersing yourself in. You can probably find that culture outside San Francisco, so move and save some money.
WhatsApp was bought for billions of dollars because they built something people could use on feature phones. That's the type of phone the world uses. There are all kinds of problems to solve outside of San Francisco, to understand these problems, move there.
Once you get your life back, take a look at your start-up ideas. Pick one. What's the next step? What's the first excuse for not doing it? That excuse is the first item to tackle. By the way, that first step probably isn't to start writing code. Finding customers should probably be near the top of the list.
This is from someone living in the Philippines with lots of kids. Houses in my area are as cheap as $100 / month. I could literally live the 4 hour work week through client work. Luckily in my case, the oldest kids are old enough that they help a lot with the younger kids. I give them a long leash to explore life without me getting in their way. There are lots of problems here which could use a good engineer.
So, don't be an engineer for engineers. Go out into the outer world and become an engineer for the people. Being among those people is where you will find your start-up ideas.