Okay, here's a summary of my interaction with Fiio customer service:
I explained my situation to them, stating that the seller in the US refused to accept my RMA (which is reasonable, seeing as they only offered 30 days, and I've had the unit for 1 year 1 month). Responses were very prompt (3 emails, all responded in less than 12 hours), in understandable English. They offered to repair my E10 despite it being 1 month past the manufacturer's warranty. I asked about the repair service and the possibility of sending the unit to a US location to get it repaired. Unfortunately a US location was a no go, and the only location I could send it to was in Guangzhou, China. As you can imagine, the cost of freight to China from US was so incredible that I could straight up buy two new E10 units instead, so I had to decline.
Still, their customer service was very prompt and courteous, overall a positive experience (even though I didn't get my E10 repaired!). I'll just go the short extension route so that I don't have to mess with the jack anymore.