The bits that stand out to me are:- they were planning and briefed for a F40 landing, however due to a problem F40 was not available, so in IMC they continued an approach, flaps 40 finally became available at 600 feet.
I think this alone should of been enough to trigger a go-around find a nice place to hold see if they could fix the problem, if not look at the data for the airport... (short runway and wet) decide if it is still a good idea to land there.. If not bugger off to another airport with a longer runway.
Then, they land beyond the TDZ in an aircraft the commander knew had a history of speed brake / reverser problems.
This is why I conclude the crew fell short of what should be expected. But the biggest failing is that of the airline and its regulator for allowing the company to be operated in this way.
It was by the grace of god that nobody was hurt, not piloting skill.
PT6A