Have I routed this PCB correctly per the schematic
No, I don't think this layout is good enough. The data sheet isn't very good in terms of PCB layout advice so you have to make a best-guess about the decoupling caps. I'd advise this: -


C1 and C2 up close to the chip with their ground returns taking the shortest feasible distance back to chip 0V/GND
Ditto C3/C4


Noticeable in the data sheet is a note about adding a 100pF to pin 4 for "additional RF
immunity". This kind of hints that the power pins will be susceptible without good decoupling and to my mind you've not achieved that. Would it be a big problem to go for a double-sided board with a ground-plane.

Also what is the advise from the manufacturer about routing from the CX pin to the cap sensor? I couldn't find anything in the data sheet (www.azoteq.com/images/stories/pdf/iqs904_datasheet.pdf)