Hi Aubrey, I hope your DOS Pi experiment worked out.
To answer your questions briefly, no the odds are this set up will not run every DOS program but it should run many of them.
And yes since rpix86 0.5 mouse emulation and support is included.
The long answer: One of the problems with DOS on the Pi is that the whole DOS PC including CPU, graphics and audio is emulated in software. A traditional DOS PC used an Intel compatible x86 CPU (8088,8086,286,386,486, Pentium/586 etc) while the Raspberry Pi uses an incompatible ARM based CPU which traces its linage to the old RISC processor designs. So this means any DOS emulator on the Pi has a lot more work to do converting the CPU and hardware instructions that are used by the DOS applications and that allows opportunities for further bugs and incompatibilities.