Well fent is about 100 times stronger than morphine so if 30mg of oxy is good for you I really don't think you should be messing around with shooting it (especially extracted from a candy sucker). The amount you get out of the candy will be quite variable, you are going to end up with a sticky unsanitary solution to shoot, fent is definitely not known for it's rush, it is a very short acting opiate so taking it IV will result in a very short high, and it's sublingual BA is 50 percent which is really not that bad.
I would highly recommend just enjoying your sucker over a few sessions as it was intended to be used. The alternative is fraught with danger and risk for very minimal gain.