Yeah, it does sound like you are naive, but it's OK! We all start out somewhere. What you seem to have going for you real well is a low spending rate and high savings already.
You should post a Case Study.
Some things right off the bat.
1) Is your spending ~20k per year? If you job security is good, it seems your emergency fund is way too high. With 270k in your brokerage account, you can basically use that as your emergency fund. The worst that can happen is having to sell off a few thousand dollars in the brokerage account when the markets are low. However, having your 50k from your MM and CD in your brokerage instead easily offsets that with more time in the market. You should have a checking account which floats 1-3 months of your expenses, but you won't need an emergency fund with an after-tax brokerage account as high as you have.
2) Your brokerage sucks. 1.5% is too high for someone who has found these forums. I second the advice to transfer to Vanguard. You can start with the JLcollins series above. A simple 3 fund portfolio with total stock market index, total intl market index, and total bond index would also work.
3) Do you have a 401k or 403b through your job now? Even though you say they don't match, if you still have access to it, consider maxing it now. You can then spend down your MM account, and effectively "transfer" your funds from your MM account to your work pre-tax retirement account. What I mean is, for every dollar you need to spend for expenses for the year, use your money in the MM account. Contribute that money which would have appeared on your paycheck, to your 401k/403b. You will end up saving more money this way as it is pre-tax also.