voluntary overtime?
Well that's a new one for Emirates. All the overtime I have had has been mandatory
To answer your questions, the rosters will probably stabilise around the 85 a month mark, with about 9-10 days off. That is from senior fleet management and not idle gossip.
You will spend most of your time at home recuperating from the effects of having flown over countless time zones and EKs schedules are such that you cannot catch up on your sleep whilst away. Inevitably you will be somewhere else at local nighttime, but Dubai daytime so sleep is unlikely. Most of us sleep on the flight deck just to catch up.
It's your choice mate, but have a good read through these pages and don't forget to read the good points as well as the bad before making a final choice. The sad thing is that there is little good written here, so searching for the positives may be a challenge.