Slow ferment followed by flat bottle

[jacksbrewery]

I have made a 5-gallon Brupack Fixby Gold, followed procedures to the letter. The overall ferment was fairly slow and then stopped at about 1015. I then decided to bottle this with half teaspoon of sugar and secondary fermentation in the bottle isnt happening.

Is it worth decanting the bottles into my Rotokeg, add some fresh yeast and Yeast Vit or am I wasting my time and may as well dump the ale!

Any thoughts appreciated!