Soldier pill do have side effect, since you are squeezing out extra strength, chakra plus it's a painkiller. Where does the extra strength + chakra come from? Your body of course, which mean you'll be exhausted once the effect wear off. The painkiller will allow you to ignore injury and push one's body over the limit thus if you are not careful you are screw once the effect wear off.

About the summoning, Kabuto need Oro's blood in order to do them (both the giant snake and then the manda), so if Kabuto is fighting alone he couldn't summon them.

Edit: Oh forgot but this came to me, instead of doing the flashy self healing jutsu Kabuto could have just do a replacement jutsu instead. Remember at the beginning of the series Kakashi got hold down by Naruto's kage bunshin and then he just do a replacement? So in my mind right now Kakashi is > Kabuto.