Do the math - you (at 95% RTP) would expect wagering that 2400 to cost you 120, so you'd be better-off carrying on. Your bonus/cash ratio shouldn't make any difference as most casinos don't calculate the bonus WR on partial cash/bonus per spin, but on the whole value of the spin which comes off of the WR.
If that's the case, find a low-variance slot and carry on and you should be circa 60 better-off than now when WR is met.
IF the bonus is only coming off on WR at 1/3 of the value of each spin (which doesn't seem likely) then you'd effectively be wagering 7200 so would lose 360 and be 180 worse-off at 95% RTP.
you forgot about the fact that the RTP on the games he played is now 600%, to get back on the average 95% you mentioned, he's is going to get broke before playing through half of the remaining wagering.
edit:
nice one goed bezig gokkie!