Your original chord is quite possibly a rootless C13. Can you show where it appears in the sequence with the other chords please?
The new ones are:
Bm - no need for the /D. The ukulele doesn have bass notes.
Em11 - sort of, probably, but it doesn't have a 7th. It really depends on context again. Where does it appear in sequence with the other chords?
B+7
The thing that decides the ambiguous cases is really what the bass is doing and what chords come before and after. Asking what chord a random shape is in isolation isn't all that useful. For example we all know that 0000 is a C6 or Am7 chord. Already we have 2 interpretations of the same shape, but if the bass is playing an F then it becomes a rootless Fmaj9.
It's a many to many relationship. You can ask how to play a certain chord and get lots of different yet correct answers and you can ask what chord a particular shape is and also get lots of different yet correct answers.
Your question of the A/C# is interesting. As pointed out, the standard open position A does have a C# as it's lowest note, but it most likely doesn't really matter which voicing you choose on the ukulele. The C# is a bass note and the ukulele doesn't really do bass. Playing the C# in the bass is another instrument's job really.
It is sometimes obvious that a particular bass line is implied. For example you might see D, A/C#, Bm. This would imply a descending bass line going D, C#, B. You'll never do that on a ukulele. The B is off the bottom of the instrument. If you're playing without a bass player, your best bet, in a case like that, might even be to make that line the top notes of the chord. 2225, 4654, 4222