Can you just call your servicer? I did my first "mega-backdoor Roth" last year, and my servicer (Fidelity) only allowed rollovers to another IRA on the web site. So I just called them up, and they did it for me over the phone. This is something they do all of the time, they knew exactly how to handle it.
And yes, you're right about the $1500 being taxable income if rolled over directly to the Roth. At the end of the year they'll mail you a 1099-R form with the taxable distribution amount listed, so you'll have to pay normal income taxes on it but not the 10% penalty. I think it's possible to also roll over the $1500 gain to a traditional (or rollover) IRA so you don't pay taxes on it at the time of distribution. In my case, I didn't accumulate much growth on the amount I rolled over, so I decided it was much easier to just roll over everything to a Roth and eat the taxes on it. But for $1500 growth I'd at least consider it - worth asking your servicer if they can do that.
Good luck!