I thought most of the online ones have a free version. I know you said it's prompting you to do the paid/deluxe version, but if you know you're not going to itemize or have credits or rental income you should still be able to just use the free one.
Also, I'm not sure how they still work because I always e-file, but I know in the past it would let you get all the way to the end and if you wanted you could just copy all the completed information onto a paper form and submit it that way rather than paying and having it processed online. So you may be able to use the assistance of an online program to walk you through the paper forms if that would make you more comfortable.
That said, I used to do my parents' taxes on paper when I was in HS and college (was the easiest way for me to make sure it was done and have the info in a timely manner for doing my FAFSA). It's really not that complicated, so I think you would be fine. Especially since you are an adult, good at math, and have filed taxes before.