I'm no expert, so take this for what it's worth...

The yolk sac looks like it's starting to firm up a bit, which kind of has me worried. The baby also looks a bit under-developed from what I see. The veins still look good, so that's promising. If it's possible, I'd try moving the baby a bit to see if you can see the umbilical cord to see if it's knotted or wrapped around the baby. If it's not, I would put the baby back in the incubator and keep a close eye on it. If it is knotted or wrapped up you'll have issues. If you can't see it, don't mess around with him too much.

Here's some info on how to handle a twisted umbilicus... http://www.worldofballpythons.com/ar...us-what-to-do/

Here's a thread that contains a video on what to do if they simply don't absorb the yolk http://ball-pythons.net/forums/showt...at-to-do-video!