Use the time for whichever developer that you have or whichever time you feel more comfortable with. The difference in times is unlikely to make any difference with your film.
BTW, back when I had my Jobo I had a similar temperature issue to yours (ambient air temperature was higher than 20C). If you want to process at 20C, check to see what your cold water temperature coming out of your tap is. Mine was less than 20C even though the ambient are temperature was higher than 20C. It allowed me to run a trickle of tap water into the Jobo water bath which the Jobo heater was able to maintain at 20C.
While D-76 & ID-11 originate from the same formula, D-76 contains an additional buffering agent that is supposed to resist the pH rise inherent in the formula over time (i.e. packaged D-76 is closer to D-76D than the original D-76 formula) and is packaged in a single package. ID-11 is distributed in two packages (The MQ in one package and the sulfite/tetraborate in another package) and doesn't contain the buffering agent (i.e. its closer to the original D-76 formula and its pH will likely rise over time).
Google for ID-11 vs D-76 and you'll find more info.