I came across this YouTube video "I Finally Tried the Low G String on My Ukulele (re-entrant tuning vs. linear tuning)". Disclaimer: I haven't viewed the video as yet. https://www.youtube.com/watch?v=TmrFHrv9ONg

I would change the tenor to the Low-G and keep the soprano High-G. Unless it's a situation of changing a single broken string, I change all the strings at the same time. It makes it easy to clean the neck and oil the frets. Also I place the end of each string under the adjacent string so in my situation it would look out of place to have a single string sticking out. P.S. it's worth the investment to get a string winder.

The general advice for forming chords is to place your index finger first and the other fingers will follow. That's generally the case for barre chords. But in this situation you are going from all open strings (Am7) to the Bm7 so what you might try is placing the ring finger on the B note of the g-string first then follow with the index finger barre. I don't know what finger picking pattern you are playing but if it involves playing the g-string note and then the c-string note, then by placing the ring finger first and playing that note, you buy yourself some time to get your index finger down to play the other three notes of the Bm. While you are playing the Bm, you can mentally ready your pinky to play the C note on the a-string to help achieve a quick Bm to C chord change..

What are the chords that precede the Bm and the chords that follow?

I suppose you could install a pickup and pipe the sound through speakers.

I think the course is complete. 16 lessons in all.

Hope that as a teacher, you also feel good about "getting through" to your students.

One reason I posed the question is when I did a search of sheet music for Row, Row, Row Your Boat, I found versions that are in 2/4, 4/4, 6/8, 12/8. It would be interesting to hear a professional singer sing the song in all the different tempos. (Side note: the reason I was thinking about that particular tune was I thought it would be an easy one to practice triplets ("merrily, merrily, merrily") and maybe even clawhammer).