It doesn't matter how fit he is (or not), ultimately it's not his decision whether he plays.
Might as well get the best wage on offer when there are no guarantees.
It says 'Net' salary. So after constituency running costs, travel, board, lodgings, food, entertainment etc etc etc are taken out.
Probably a hundred quid a month will be 'donated' - then that will be used as a tax write off somewhere else!