Rocking and rolling now...
I think you may be a little bit hung up on the idea that you need a CTO. Consider that what you think the title CTO represents and what a CTO actually is may not be the same thing. Instead of concentrating on a title, start by making a list of the specific tasks and functions you need help accomplishing. Maybe all you need is a lead developer with whom you can communicate well, making sure you understand what's happening with the development team and setting expectations that are actually achievable.
What follows your list of requirements is determining the resources required to obtain the skills on your list. If the answer is that you have to pay salary to everyone working on your product, instead of trading some amount of salary for equity, how would that change your product plan?
On the surface, it sounds like what you've lost is the channel for making things happen, not the plan, not the intellectual property, not any code, not a piece of your company. And in those terms you're pretty lucky. You're just distressed by the timing setback in finding a replacement path to executing the plan you've developed.
Fortunately, unless there's some pressures you didn't reveal, you have infinite time to move forward. This is still planning time. It sounds like you got some initial validation, so it should be easier to persuade another talent to step in where one has left the seat vacant. What you want to be sure of is that the layer of skills you had assigned to the previous CTO role isn't something essential to getting the job done. For example, if you don't read code, it's probably not a good idea for you to supervise a remote developer team. If you want to move forward with the remote developer team you already scoped out, my first suggestion would be to approach some of the Vietnamese Community Organizations and tell them about your situation and that you're looking for a technical lead to manage a team you found in VN, but someone who is available to you here. I don't know about your part of California, but here in Boston, I could walk down the street and have that meeting easily.
There are several things above for you to consider, but I suspect the best path forward is going to be hiring a domestic lead developer for your remote team, and not distributing equity as an incentive for work.
I think you have to find a tech person who really likes your idea and believes in it. So he/she can focus on the technical solution and you can cover the business side at the same time. I would not recommend dealing with contractors yourself since it would be a major risk to lose your money and do not achieve what you actually want.
From my experience slicing pie model works the best when company shares are split according to contribution (time, money, connections etc.).
Would be glad to talk with you about your project.
I would suggest have your friend fill in as temporary CTO if he is dependable, but work out the contract, your friendship should not suffer because of a business dispute I have seen many such friendship broken. You can in parallel hunt for a full-time CTO, get someone with a more generalist who have a bigger vision, preferably with at least one startup experience. Another alternative is to reach out to companies in India / Vietnam or Philippines who help build teams for you. Now I do not know what is your budget you can get connected with one of these companies who can help to set up your team and get it working. In the initial phase you own the payroll, help you with the initial product launch and then once your are standing on your own, you can spin off.
But again with coronavirus everything is very difficult hence first thing I would suggest is to wither this difficult period. And also search someone with experience because an experienced guy can help you in longer run.
well see it as a positive. the simple fact that the ex-cto suggested that you need 2 fullstack developers with "Backgrounds in MySQL or MS SQL" was one of the worst decisions you would have done. No one in ML / AI uses MySQL / MicrosoftShitql