Editing this post because with the incoming feed hardwired directly and bypassing the Spectrum modem I have lost phone signal. I am now back incoming signal with splitter going to both my modem AND Spectrums modem
You should have mentioned that you have there home phone service as well. If thats the case then yes you need the spectrum modem but at that point it is being used just for the phone.
Have you hardwired your laptop to the router and run a speed test? Is it good?
Have you checked if there might be a firmware update for the router?.
Have you rebooted the router? Is the wifi still bad after that?
If after all the above has been done. Try changing the channels on the router.
Report back then