Here are FAA Holdover Tables, which should answer question 2.
http://www.globalspanaviationgroup.com/FAAHOT.pdf
Question 2 is dependent on whether the wing is cold soaked.
About Question 1, I would return to the gate or wherever I could do a "hands on" check. By the time, you go outside and check, you'll need to get de-iced again, anyway.
GF