Nope. I'd most likely apply for something I believe will be enjoyable 8-10 hours a day, Monday to Friday from January to December. It's called employee retention and you should evaluate that metric yourself. If you let your employer handle that part it'll be about knowing how much will be your next salary increase. Which falls back to your question. Short term versus long term.
Go get a job you're not an entrepreneur. People will constantly tell you - what you do sucks. It's rule number one in the wannabe-entrepreneur world. If you can't handle that part I'd suggest to go get a job. Otherwise, move one to step #2 - focus.
setup a meeting with them. See what they offer and try to get some info about their vision and strategy. If the deal is to weak then turn it into a "nice to meet you let's chat about our progress in the future". If it's a good deal then you'll be in a better place to answer your own question.
Just an email with "are you for sale" means nothing. You shouldn't even read it unless you're willing to hear about a potential offer.
Take the manager role. It's the hardest to get between the 2. There are many great companies and a zillion individual contributor positions out there. Stay in that company for 1-2 years and apply at a better company as a manager. Stupid recruiters will look at your current title. So either move horizontally or vertically...
Taxes. Taxes. Taxes. As a single individual making a little over 200k you endup with 120k net. The gross income means absolutely nothing since you're giving away 80k every year.
At this point you'd be looking to take %50 of the company just by having an idea. The rest (%99 of the job at that point) will have to be handled by your tech co-founder. Plus, you'd be in charge of telling him/her when to deliver and how.
My best recommendation is to start your "CEO" job earlier and to land an appointment with an investor willing to invest in your idea and to include your potential co-founder in that meeting. That would make you worth %50 easily.
A college kid with zero savings can become billionaire. An old rich billionaire can spend millions of dollars trying to build 100 products people don't want. There's no right answer to your question. The only advice I heard that made sense to me was:
%99 of the people are looking for: security, then comfort, then becoming rich
%1 of the people are looking to becoming rich, then comfort, then security
It's not about the value the day you file for a divorce. It's about the value he had during the marriage period. Selling shares right now won't change much.
It seems odd that you owe the actual cash money. Are you %100 sure about that? 50/50 is not related to the value of the shares but the shares themselves.
In this case (you don't owe any cash), even splitting your shares in half might end up in a big pile of cash if your company is really successful.