I passed the JLPT N1 in 2012 and have been studying consistently since then.
The JLPT1 is valuable. Many non-Japanese look down on it, but it's how the Japanese government itself assesses competence. It's not the be-all and end-all but it's useful.
At this point I'm mainly just reading books and watching television in Japanese.
Translating is a very different thing to reading. If you want to get better in translation, do more translation.
Here's my question: what are my options for learning how to translate outside of a formal education?
By starting to translate. Personally, if you feel you need an extra bit of paper I wouldn't spend money on something like Simul, but instead invest in some kind of academic qualification, maybe part time.
but at a minimum I'd like to start trying to educate myself on translation to see if it's possible.
Hmmm. I diagnose preparation paralysis.
I've been practicing by doing some translations on Gengo.
Good. We all start somewhere. The more you do, the more you learn.
I majored in engineering in college and worked as an engineer for a couple years, but am currently freelancing in the commercial production industry.
This is potentially very useful for translation. However, I find it odd that, having invested in a completely different education. you are so interested in translation.
Unless it's a very 'soft' engineering degree I suspect you would earn more being an engineer than you would as a young (?) translator with very little experience. And if you're a translator you'll definitely earn more if you already have long experience in engineering to show people.
Why didn't you study translation at college? When you say you're interested in translation, is it really that you're interested in Japan? Because if that's the case I would suggest that you find a route to Japan rather than totally change your career.