The one thing that immediately caught my eye is the lack of fixed-width-ness (for lack of a better term) in the value displays. IMHO besides being somewhat annoying to read it can be rather misleading, which is bad especially for something "designed specifically to use as a teaching tool". It's misleading because it doesn't show that the storage for the values is fixed-width. For example, this clearly shows that the registers are 32 bits and never anything but:

    R0 0000BEEF
    R1 000BEEF0
    R2 000000BE
    R3 00000001
    R4 BEEF0000
    R5 00005F77
    R6 00000000
    R7 00000000
    ...

I've taught Asm before and seen so many students get this wrong that it's worth calling out. In fact the right example under the "Error Correction Suggestions" section gets this wrong too --- that's an assembly/syntax error, not a runtime error. (ARM's immediate value encoding is also worth looking at if you haven't seen it before, since it's not just a single 32-bit value either: https://alisdair.mcdiarmid.org/arm-immediate-value-encoding/ )

The other thing that I'd suggest as an improvement is a 16-byte-hexdump mode with ASCII on the right for "View Memory Contents". Other than that, with perhaps the exception of "infinite loop detection", the other features look useful.