I'd imagine the best way would be to state the facts somewhere (say, in a subpage to your userpage, or perhaps in an Appendix page, with a title like "Proto-Balto-Slavic correspondences and examples" or something more to your liking), -- i.e., what you mentioned above about the correspondences, perahps a little more elaborated and with examples, or with a table of correspondences for PS, Lithuanian, and perhaps Latvian, if you prefer, showing which correspondences are the same, which aren't, etc. Then you refer back to this page in footnotes. So you would add a footnote to the *duwō page, just as you did with R. Kim's reference in, e.g., *leipā, except in this case the reference would be to CodeCat.
Alternatively, you could place the facts in the page for *duwō itself, say in the etymology section. But this strikes me as inefficient, since the facts would be the same for other PBS words that had the same phonemes. In fact, one would have to add a discussion PBS and PB phonemes to all PBS reconstructed protoforms. Why not put everything in one place, and then simply refer back to it in the footnotes?