So my credit would be free from any mortgage (although I am on the deed).

As still being 19 my credit is still establishing but making sure I pay everything on time and taking care of it.

Can any lenders out there educate me on whether there is such a thing as 5% down, low credit score (low 600's) jumbo loans?  

There are no shortcuts to building credit, it takes time.

More info in the link below.https://www.biggerpockets.com/forums/521/topics/605679-september-2018-christyna-romero-credit-specialist-ceo-of-crt

We both have full time jobs, our credit scores are very good, and we have some savings.      

(See American Housing Survey Reveals Rise in Doubled-Up Households During Recession and For Many Families, Bad Times Require 'Doubling Up'.)And there was also a fear about jobs/income and credit.

3) Is there a usual or standard amount/percentage for the Option Fee, rent credits, and any other fees/charges?

Read "Rich Dad Poor Dad" right out of high school and bought my first place shortly after while still living with my mom and going to college.

If you haven't already, it would likely be worth your time to start having conversations with some of your local bankers / credit unions about your options around conventional financing vs.