I also have a passion for researching and collecting late war bayonets. Keep looking and you will find all the codes. Production remained high in 1944 and many were captured and ended up in the US. They're out there, it can just take time. I think I remember when you were selling some pieces on ebay a few years ago.
Regarding the frog. You do see the Ks98 frogs on these bayonets occasionally and anything is possible. For the most part however I suspect the Germans used the correct frog, especially for the S84/98 as they saw heavy use. More inclined to believe that the incorrect frogs were added by veterans or postwar owners, dealers, etc. My thoughts only ....