1. Place a 30 amp, double pole switch between the terminal strip and the SSRs. In this manner, you will be able to turn the element off with the flick of a switch. Also, with this switch, two SSRs are not necessary - one will be sufficient.
2. Is your PID rated for 240 VAC? That is how you have it wired.
3. You should move the inline GFI to the powercord end of your system.
4. Ground everything. The kettle, the double pole switch, and the enclosure should all be grounded.
5. You may want to add a switch to your PID.
Lastly, have an electrician or electrical engineer review the project before you plug it in.