Don't have to worry about fixer, it lasts much longer than you expected. I made 1 gallon working sol. back to about 8 yrs ago, but I don't have chance to shoot or process since then. I processed few rolls these days and it's still working.
As it can wash off unexposed silver halide on your neg(clean neg), it is working!!!
Your problem is dev. If it's stock sol you were making, and stored in cool dark place, it may last longer. If it's working sol, it may only last for couple months.
When it's turn brownish tone, the only thing you can do is dump it to the sink
Since you have very little qty to process, best you can do is to
1, store it in air tight btl
2, shoot as much as you can
3, make only enough working sol each time, and use it as single shot developer.
4, go for HC 110, or Rodinal.