Two Plus Two Older Archives - Help with the final table crapshoot

Having just read HoH, and thanks to the great discussions on these forums, I feel my MTT play has come on loads over the last month. In 28 tourneys this month ($10-50 buy-in, mainly 100-300 players), I've been ITM 5 times including 3 final tables (I realise this is a very small sample).

I've regulaarly found myself amongst the chip leaders towards the late stages, and have found a confidence I lacked before.

One thing I still can't get a grip of is the last few places. All of the money in these tourney's comes in the first few places, and rises VERY steeply. Last night the prize structure was something like 700-500-300-200-100-80-70-60-50-30-30-30-30...30 (18 paid).
By the time I reached the last 5, every pot was potentially worth $100, but the blinds had reached the point where the whole thing seemed to descend into a crapshoot.

Is there a sensible way to approach the very late stages? Or is the only answer to get the chip lead while there are 20-5 players left? It seems that to be devoid of meaningful strategy at the part of the tournament which determines how profitable the past 3 hours have been is a major leak in my game.

Anyone care to comment on the last hand?
5 left. I have just around 20k in the BB (1600/3200 blinds). UTG has 30kish, CO 70k, Button 3500, SB 60k.
Button has been trying to outlast me, but I've managed to hold up my stack for the last few orbits. SB has been playing very well, aggressively buying/stealing pots.
UTG is very tight, CO playing well, not nearly as aggressive as SB.
I get 93o in BB. Folded to button who pushes. SB flat calls, so I call for 339 more. Flop 987 rainbow. SB pushes. It seemed to me that I only need to worry about beating the button here. If we both go out, I get 4th. If I fold, I'm favourite to get 4th. If I win, I'm playing for first. Am I correct to call?

Results in white :

<font color="white"> SB had K6 for OESD + overcard. Straight completed on river and I get 4th. </font>

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