Bollocks - found out today that I probably (I could always die beforehand, I suppose) have to move to Singapore sometime next year. Anyone from Singapore? What's it like? I'm so depressed right now, I hate packing and I probably have to go on a 'moving to Asian country' diet!
Cullen is great and pretty etc, etc........too depressed even for Cullen thoughts to cheer me up. 
Best of luck with your move! I'm sure it'll be challenging, but it's also a pretty amazing opportunity, and I hope it will be a positive experience for your family. 
If Meredith lied, then yes - it's possible he didn't know at the moment, when Hawke was leaving. But with Anders shouting in the middle of Lowtown, no way he wouldn't know it shortly afterwards. Must have been tough for his moral and duty principles, knowing that he let person, responsible for blowing the Chantry, go unscathed.
Would the powers that be necessarily know Cullen should be able to recognize Anders on sight? They'd had prior dealings, but it wouldn't likely be anything important enough that there was an official record indicating they had met. It seems like Cullen could handwave this by just saying it was "some mages" he let go by necessity; it would be reasonable for anyone receiving his report to assume he didn't know that one was Anders.
I'm sure it was a tough choice for Cullen on a personal level, though. He didn't have to make it in my canon playthrough because Hawke killed Anders (with great sadness and regret.)
Did Meredith know there was a difference between the idol and regular lyrium though? I mean on a rational level. She obviously had the idol melted down and somehow fused with her sword (I'm assuming she didn't take it into her body in any way.) The idol made Bartrand mad with jealousy, and he wanted it back from Meredith. Would she have freely and willingly distributed it amongst the Templars?
I don't think Meredith would do so willingly, but I also think the red lyrium itself may have been a factor. If it has some degree of sentience - even if it just propagates itself instinctively like a virus - it may have been instructing her to spread it. It would make sense that Meredith would receive that instruction and Bartrand wouldn't, because Bartrand is sort of dead end for a spread of lyrium, whereas Meredith is in a perfect position to "infect" the other templars.