It used to be that you could get stems in longer & shorter lengths as close together as 5mm; lately, I've only been seeing 10mm differences in stem length. Either just a TOUCH moe upright or a SLIGHTLY shorter stem will help the neck issue. I had a similar issue a couple years ago, and the bike I was riding at the time had a frame failure, which was ultimately a good thing. The bike I ended up with had a 5mm shorter top tube, and a 10mm shorter stem. 15mm total difference may SEEM small, but 2mm can change the whole character of the bike!

I'd try a 10mm shorter stem, and set about 3mm lower.