Nah, while cycles/instruction where indeed fixed in those days (and for some time yet to come), it was not necessarily 1 cycle but rather depended on the instruction.
Indeed. I used this algorithm on OS/2 1.0 as part of a GUI (OS/2 did not have a GUI until 1.1). That was on an 80386. MASM came with a nice ring-bound A6 book which summarised the instruction set, including timings. I seem to remember that 3 cycles was normal for a short instruction, but many were considerably longer.