Can I use a current divider to protect my IC?
I think it is more likely that the missing flyback diode from your solenoid is causing the problem, however you do also need one on the relay as other suggest.
The relay is currently connected to the same power supply as the 555.  You say that when you also connect the solenoid to the same power supply you get the problem, so it must be a spike from the solenoid that is damaging the 555.

Add a flyback diode to both the relay and solenoid.