I don't know, you shouldn't 'expect' multiple miracle 3s from your opponent at the end of each close game. I respect the Heat, but one miss in each of these last two games and the Cs are 2-0. I know they've been doing it all playoffs, but it just isn't normal.
But it really shouldn't have come down to this. You mention that the situation is fragile, but unfortunately so are the Cs. The awful reset on the 24 second clock led to a 4 point play, a no-call on Theis' lay-up (when he got smacked in the face), and then another 3 point play. Instead of shooting FTs to go up 12, it was suddenly a 3 point game in less than 30 seconds. Rather than fight back and build up their lead, they continued to wilt and somehow fell behind by 8 just a few minutes later. It was the same reaction as when they lost game 3 to the Raptors at the buzzer. They just couldn't get over the miracle play and lost game 4, as well (despite having a half-time lead).
Somehow MIA doesn't have this problem. It's not like they aren't young, they count on 3 rookies (Duncan is 2nd year, but he was D-league last year) and Bam is only in his 3rd year. The bubble being in FL may actually be a real benefit to them - they are used to the scenery, the setting, the weather. And their home crowd sucks anyway. They would have been the away team in all 3 match-ups so far, but they have benefited from a neutral court this whole time. I imagine the miracles will end if/when they face Lebron and the Lakers (of course), but they literally play like they are just in a pick-up game each game. The pressure doesn't get to them at all.