1: already answered. JIT = as fast possible, uses all available CPU cycles without hack (Idle-slider in CPU-tab) that detects 680x0's STOP-instruction and waits a little.
2: -f <config file> -0 <path to adf> (-1 = DF1, -2 = DF2..)
3: ISP software? I feel your pain...
Does it stop crashing if bsdsocket emulation is disabled?
4: press SHIFT+F12 (not recommended in fullscreen mode..)