You have a lot of cash right now and the amount you need probably depends on your levels of income and spending. If you don't mind sharing:
- What is your current level of income? How much of it would you say is stable and how much is unstable?
- What are your current expenses? What proportion could you cut back on if you really had to?
- What do you reckon your income will be in a few years time and how long do you think it will take to get there?
- Do you have any emergency sources of cash/credit/goodwill you can tap in an emergency? This can include stuff like family support, government support, credit cards, lines of credit etc.
How much you hold depends on all on the above but deep down is a matter of personal choice. If your life is stressful right now you might want to keep a bit more cash so you don't need to worry about running out. However if your financial situation is more stable than you thought then you might want to fill the Roth.
As far as holding VTSAX, you're doing about the best an uninformed investor can! I would leave that alone until you have at the very least read the investment guides you listed. Better to lose out on making a bit of money than to make an unforced error and lose a lot
i. My earned income is about $500 to $700 per month. It is being held down right now because of several factors that will gradually become non-issues over the course of the next year. One of those is child transportation, and that issue will be resolved in June, at the latest.
ii. My current expenses are (well, will be by next week when I move...) just slightly less than my earned income and support income combined. In a dire emergency, I could cut about another $200 to $300 per month in expenses, but it would mean eliminating important things that I consider worth the money for now, like counseling.
iii. I don't have a real feel for where my income will go, but it will only be restricted by parenting and other circumstances for about a year.
iv. I have about $10,000 in available credit, and a great family. My kids and I have been living with my parents rent-free for sixteen months, and will always be welcome.
It seems that there are a lot of votes to keep everything in VTSAX, so I think I will leave what's there alone, and if I do add anything, it will be more VTSAX for now. I can always add a bond fund later, when I figure them out.