Desultory, here means, 'in a casual and uncommitted way.'

Eccentric means strange or out of the ordinary but I am not sure of the other word

It means he's not taking his studies very seriously...

They mean that the author is as mad as a hatter; using such inappropriate language where less supercilious wordage would suffice, nay improve the turbidity beyond all. 'Methinks they did prevaricate too much.' and for scant reward.