I guess it will boil down to trying to balance your social life with how long would be fair to leave the dog alone, as well as will it have enough stimulation when you are not there to stop boredom, and ensure you dont come home to chewed furniture and pee/poo over the floor as it couldnt wait any longer.
That is why my bf (or rather me, because i am at home in the day) now has his dog more than his exw, as he was left alone from mon - fri for 6 or 7 hours a day, then when her social life picked up/she started a relationship with her current bf, she would come home from work for maybe an hour before she was off out for the evening.
My bf said he didnt think it was right for the dog to be alone for such a long period of time (and i know from having him here, that even if he is left for just a few minutes, i will come back to see him sitting at the door looking through the glass waiting for me to return, he hates being left behind), especially in a tiny 3rd floor flat with nothing to occupy himself with, and so for the sake of the dog's happiness he now stays with me for 90% of the time. He has 2 other dogs to play with , a garden to go in and out of at will, and if i go out its never for more than an hour or so at a time, and i pretty much dont go out in the evenings , so there is always someone about.
His exw loves the dog and misses him being there, but she acknowledges that it isnt fair on him being alone for so long so often, so she now has him for a few days every 3 or 4 weeks instead.
Is your dog ok/used to being alone or does it get anxious? Will he be a dog who will whine/howl if you leave him?
If you are able to get back at lunchtime to check on him and let him out for the loo etc, then he may well be ok being left for the rest of the time, but do you have anyone who would be able to pop round if needed? For example if you had to be elsewhere one lunchtime? Would a local dog walking/ sitting service be a possibility?
You clearly love your dog, but do you think you will be able to give him the attention he will need if your wife will no longer be around to share the responsibility?
Also, if you will be renting, will the landlord allow pets?
Hope you find a way to sort it out , good luck