Help - short sale questions

Newbie in real estate investment trying to close first rental home purchase(it's a short-sale).

This short-sale home(only 1 lender) was listed for $170K, we offered $162K ~6-week ago, seller accepted. Listing agent just informed our agent that lender counter $166K and if we accept, lender consent will be available early next week, and expect to close escrow before end of march. Our agent told me $166K is a very good deal(their CMA shows fair value of $180K for this home, but I think it's in the range of $162K-$172K), and normally when lender counter in a short-sale, that means lender want to meet a bottom-line #. She also told(which I was able to confirm on-line) me this home has a auction date of 3/23/2012(postposted from 2/23/2012 - was it because of my offer which was sent in mid-Jan?), so if we don't agree to the counter offer, lender will just go ahead & foreclose this home.

Questions:

1. Does it sound right that lender only counter to meet a bottom-line # in this case. Since there's only 1 lender in this case, I'd assume the bottom-line should be relative flexible. Also with the 3/23/2012 auction date, I suppose the time pressure if on the lender. So should we insist $162K is my best offer, or should I buy into what my agent said and accept the counter offer? Anyone who's experienced in short-sale can offer insight and suggest how to best respond to this counter offer given the situation.

2. We just found out this weekend that this house has shingle roof, not tile roof as described in the listing(we did visit this home with our agent ~6 weeks ago. was there for ~10 minute, but didn't pay attention to the roof. BTW, home interior was very nice/clean, owner seem to have taken good care of it). What to do when home is different from listing description? We sent an email to our agent, but haven't heard from her. should we ask for a price reduction(like $2k?) for the difference in this case, or should we wait for the inspection report then file an addendum? Anyone have any suggestion?

Thanks in advance!