Hello,
1) We don’t see any issues with the customize button for the mobile device
on the home page http://prntscr.com/qbmusq
2) We don’t see any issues with the customize button for the mobile device on the single product http://prntscr.com/qbmtm1
3) Too much information for the mobile, Sticky Add To Cart Bar feature is not very suitable for your products because of the information that you have for them. We have disabled option http://prntscr.com/qbmwtu
Regards