First problem can be fixed by turning on loop_context_vars and using the following:

<TMPL_VAR NAME=ID>: <TMPL_VAR NAME=NAME><br>
<TMPL_LOOP NAME=CATEGORIES>
<TMPL_VAR NAME=ID>/<TMPL_VAR NAME=TITLE><TMPL_UNLESS __last__> | </TMP
+L_UNLESS>
</TMPL_LOOP>
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As for the second problem, I don't see another way around your problem beyond what you already have. The template is just presenting the data you gave it.