I have a few questions to help assist you with potty issues:
1) When was he neutered?
2) Can you describe his routine a bit?
3) How much time does he spend outdoors and do you go out with him?
4) How was he initially potty trained? Crate? Enclosed area? Potty pads?
5) Does he go to the same spot? What do you clean it with?
Your not doomed. We just have to take a few steps backwards again. This will entail you taking him out on lead or going outside with him and staying there until you see that he has gone. If he hasn't he will need to go back into the crate until you take him out again later, etc. If he doesn't eliminate outside then he doesn't get to roam around in the house. It is a must that you take him out and stay with him until you have seen him go. This will not only help to prevent accidents in the home but it will also help you figure out a routine that works for the both of you. Eventually, this will become a habit. In the house he isn't to be out of your sight for not even one minute. If you have to keep him on a lead then so be it but gates usually help to keep him in your sight. If he has an accident and you did not see him do it there is no sense in reprimanding him, only you. We are starting from the beginning. However, if you do catch him in the act you can yell NO, pick him up and take him straight outdoors.
To clean up the messes you will need an enzymatic cleaner like Equalizer or Nature's miracle. Vinegar will not remove the odor that he can still detect.
As to giving out clues. Try a bell hanging from the door knob. Make it low enough so that he can reach it. Everytime you take him out to potty you need to ring the bell. Many dogs pick this up rather quickly and will ring that same bell when they need to go potty.
Let me know if you need further assistance.