Re: #3, tradeoffs of lucid dreaming,

I don't know of any studies to support this, nor have I done sufficient systematic investigation of the phenomenon, but I am a lucid dreamer, and I have noted a general trend of increased alertness and improved memory of dreams after lucid dreams. I'm not well-versed enough in the science of dreaming to propose any credible explanation for this, nor do I have evidence that memory in general is improved. However, it has been consistently true that I have better memories of lucid dreams than non-lucid ones, and I am more likely to wake up fully alert after a lucid dream than is normal for me.

I know anecdotal evidence may not carry a great deal of weight, but I hope this is helpful.