Can I convert KrisFlyer points to Starwood Preferred Guest? Can I transfer KrisFlyer to anything other than Virgin?
Unfortunately no you can't convert KF miles to SPG points...
The only miles you can convert KF to are virgin as you already pointed out.
You can use KF miles on SQ partners though if that helps: http://www.singaporeair.com/en_UK/ppsclub-krisflyer/redeem-airpartners/
Or you could convert them to VA points and use them on VA partners like EY, HA