Well, relative and absolute internal linking is pretty much the same, they are not duplicate and they do not change anything when stealing content.
Of course, if someone would want to steal content, he could use you page as is with only relative links, where with absolute one he'd have to change the domain to his, but, this does not really make any differences since we can mass search and replace ...
The base href would only be required in case you'd be using broken relative links, for example when using virtual folders.
To conclude, if your links works, to does not really matter if they are absolute or relative, as long as they work, it's pretty much the same.
Now, some will argue that repeating your domain name can help out a little for the domain keyword density, but i doubt it makes a really difference SEO wise.
The real matter is are your link working
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