As long as you are not in the low 50's where the yeast could go dormant, you are fine.
I think that they recommend certain temps to achieve certain flavors that they describe. Ales, will ferment fine in the low 60s, just slower.
Could be. But I almost always ferment cooler than they recommend. WLP023 Burton Ale, for instance, says 68-73 and I tend to ferment that at 66-67. Not a large difference. But that one's already very, very fruity. Can't imagine fermenting it at 73. I think Wyeast generally says 60-72, which I'd consider a better indicator or the safe zone for ale yeasts, with some variation in flavors of course. I tend to use 64-68 myself though (except for Belgians).
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