dCore x86 release candidates have been updated with a fix to properly deal with extra repo DEBINX files when they contain entries for more than one architecture, ie both i386 and x86_64.
On dCore-wheezy, the wget and ca-certificates packages need to be imported and loaded to make use of https extra repos as it's version of Busybox wget does not work with https extra repo entries. dCore-trusty and all newer dCore ports have a version of Busybox wget that works with extra https repos.
http://tinycorelinux.net/dCore/x86/release_candidates/