I can just see a V8 unit around the corner allowing you to dose everything individually
Regarding the syringes getting stuck, you will find that syringes are not made for long term use. The rubber plunger will loose it's lubricant rather quickly and will tend to get stiffer with time, meaning the likelyhood of it jamming up. I would suggest lubricating the plunger with silicon based lubricant, the same you use for O-Rings and pump impellers. Once a month should keep everything moving freely. It may even help get a larger syringe to work for you with the existing motor.