>>25551528
keep the job, take less hours at the same rate (which is also a signal to them that you cannot be exploited)
chances are that they cannot do the same work in 30% time, so maybe they have to increase your hours again.
find a 2nd job (around another 50h), now you have the time
also it's good to gain new experiences, new environments - maybe you like the work elsewhere better even - and you are prepared if they actually fire you from your 1st job