Uhmm, you do understand how to eat to gain weight correct? I just don't see why you are stuck at 160lbs. Are you following a trianing program or something you made up/found in a magazine?
250-500mg should be fine. If you decide 500mg, shoot 250 sunday night; wed morn or vice versa. You will gain ~10lbs of water fairly quickly without an aromatase inhibitor, face may get puffy, pants get tight.
You should have everything needed on hand before the first injection, 'cause running out or needing something halfway through is bad news.
clomid will work for you p c t. week after your last shot take 50mg ED for 4 weeks, doubt 250mg will shut you down too bad or need H C G. You should only need H C G if you notice your testicles withering away.
I have an emergency kit of sorts, just in case of sides. Nolvaldex - tamoxifen citrate - , clomid, HCG - human chorionic gonadotropin - , Femera - letrozole - , cabaser, a-dex, and AIFM. Haven't needed most of it so far, but better safe than sorry IMHO.