He lied to you. 850 is the highest score possible and fewer than 1% get a perfect score.
Do you understand that a credit score is a record of your credit use and that when you deal mostly in cash, there is very little to score you on? You are probably as high as you are because of those past car loans that are paid off. But you have nothing else. It is time to start using some credit. Get two cards and start using them to buy, as much as possible, the things you have been paying cash for. Keep track of what you spend - which you can easily do online with your cards - so that you know what you have to pay when it's time to pay. Pay the balance in full before the due date so that you don't incur interest. Maybe use one card for your everyday spending and use the other card to make utility, and insurance bills.
If you're making it fine on $4k every month to spend, get that $30k out of the bank and get it invested into something that will earn more than the almost nothing you're getting at the bank.
Investing is a separate issue, but you need to invest.