Re: Threshold problem
If it were me I'd either use a metal nail on transition strip (kinda tacky ) or just surface nail a wooden transition strip in place. Normally, transition strips of this nature are kind of "T" shaped. Since you don't have a gap between the two, you could just use more of a "scribe" molding across the space. This would look much better than a metal transition strip. If you really need/want a traditional "T" molding, then cut the wood back enough to accommodate one. A circular saw will make the majority of the cut while a reciprocating saw or handsaw will make the ends of the cut.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!