Aldrich tell you the PDI (polydispersity index) < 1.1. The PDI, equal to Mw/Mn, is a measure of the breadth of the MW distribution. A value < 1.1 is considered very narrow; essentially you can treat it as if all the chains have the same molecular weight.
For the extended length ("contour length"), consider the backbone carbon chain. What is the length of a repeat unit if the C-C distance is 154 pm and the C-C-C angle is 109°? How many repeat units are there in a molecule of MW ca. 5000?
For the coiled length (not sure what you mean by this - radius of gyration?) - depends on solvent quality. Bigger the better the solvent.
I used to do quite a bit of polymer characterisation, but since I left that company I haven't got access to the books, and don't remember all the equations.