I'm slightly envious that you get to live in an RV! I'd love to be able to work remotely from a campground in a national park.
Here are some things to think about:
1. I think investing the money is of course a wise decision. I am assuming you have no debts now.
2. Consider maxing your contributions to your work plan, especially if your work plan has reasonable fees. On top of that you should be able to contribute $6000 to a tIRA and $6000 for your spuose to their tIRA. See
https://forum.mrmoneymustache.com/investor-alley/investment-order/3. Some believe that time in the market is more important than DCA. My personal opinion is get the money in the market.
4. Maybe someone more advanced than I can answer this for you. I personally think mutual funds are simpler in that with Vanguard which I use I can buy fractional shares with a mutual fund but cannot with ETF. Either way, I own both.
5. It's up to you. Are the fees decent? Does it bother you to have your money in more than one place?
6. Assuming you have no dependents, I would look into the tax advantaged space as well as using Roth ladders to provide yourself money when you retire.
7. What are your plans for health insurance? Is your spouse going to continue to work since they are a bit younger? Are you planning on living out the rest of your days in an RV or will you need to purchase or rent a home again?