How many individuals do you know that would actually tell a prospective employer that they smoke weed?
And I know nothing of Fifield's academic work history. He's clearly inventive (I.E the pups). The fact that he is eccentric is practically commonplace amongst scientists. I had a biochemistry teacher who used to dress in short shorts with socks and sandals, and who used to carry a dead squirrel with him. He's one of the most cited biochemists.
As for the rushing thing, the time lapse in between Shaw and Holloway discovering the pictogram and the arrival time, plus the time lapse necessary for publishing a thesis (which, trust me, isn't quick) indicate that it would have to have been rushed. Plus the fact that they don't know each other and haven't trained together is another indicator. And his own personal preparations, getting a ship ready, putting the word out for the crew of 17, getting the equipment ready...it all reeks of a rush job.
Plus, you know, Weyland's almost dead, so there's that reason to rush.