May I offer a Slavic perspective to the T/D confusion. I believe you are both right. The T/D spelling causes many spelling mistakes even by Slovenian speakers, and with foreigners, even more. Only Slavic people can spell my name correctly, but others most often spell it as SUEDKA. You can imagine how much more confusion it was in the Middle Ages.
There are many Slovenian words that are spelled the same and have different meaning. There are words that are pronounced the same and spelled differently: this would be most frequent mistakes in the VM since it is written in phonetic orthology. Slovenian speakers can understand the meaning from the context: When POD (pronounced as POT) is followed by a noun, it cannot mean granary - POD (also pronounced as POT), nor POD - floor, bottom (also pronounced as POT). Various grammatical suffixes could be tried to figure out etymology, like POD (POT - floor) and PODEN (alternative for POD/POT - like German Boden). POT spelled and pronounced as POT could mean perspiration or path, road. POT POTITI means perspire, PO POD/POT PODITI means 'chase on the road'.
The reasons for this confusion are the sound changes that often affect the root (making voiced D into unvoiced, or voiced T into Unvoiced), and the similarity of the pronunciation of those sounds, causing spelling mistakes (even consistent one)
Understanding etymology is also very important. Slovenian word TROSTAT is in fact Slovenicized German TROSTEN - Trost + (geb)EN (consolation give) thus became Slovenian TROST + (D)AT. In a similar way, German THAILEN became TALLAT in Slovenian. The alternative Slovenian word for divide is DELIT (DEIL is like German THAIL) + suffix -IT. By adding suffix -i to a verb DELIT/DELID, we get DELIDI (Latin Y was changed in Slovenian to either i or j). It is possible that this mistaken rationality, based on phonetic, is the reason for all those VM suffixes -dy, since there seems to be no suffixes -t or -ty (for infinitive). There are also many Slovenian suffixes for different Slovenian grammatical forms, that could result in so many EVA -dy endings.
The copied words are taken from the 4-way German, Latin, Slovenian and Italian dictionary, and the darker pictures from the German Slavic Etymology book.