How often are you in situations where you have two choices: option A gives you 1000000 units of happiness, and option B gives everyone on this planet 1 unit of happiness?
Probably rarely. But you and I are in a position where someone, somewhere, would get more units of happiness from our efforts than we would. You could be working night and day, without let up, to feed the hungry, to vaccinate the unprotected, to shelter the exposed,..
That is your lot in life, under the Utilitarian God. That is the debt you owe. And if you don't pay it, day after day after day without let, without any hope of relief, you're evil in his eyes, as you are in your own, as long as you choose to worship him and are consistent in your mind about the debt of servitude you owe.
Trying to maximize ethical behavior under utilitarianism would probably mean getting as much money as you can, and giving almost all (as much as you can, to remain able to do your job) to the most efficient charity. You can spend money on yourself only as much as is necessary to keep the process running; same about free time.
You are correct about the de facto servitude. No excuse for luxuries while someone else is suffering. (Except if you could show that enjoying the luxury increases your productivity enough to balance the spending.)
Utilitarianism seems to indicate that the greatest good for the most people generally revolves around their feelings. A person feeling happy and confident is a desired state, a person in pain and misery is undesirable.
But what about taking selfish actions that hurt another person's feelings? If I'm in a relationship and breaking up with her would hurt her feelings, does that mean I have a moral obligation to stay with her? If I have an employee who is well-meaning but isn't working out, am I morally allowed to fire him? Or what about at a club? A guy is talking to a woman, and she's ready to go home with him. I could socially tool him and take her home myself, but doing so would cause him greater unhappiness than I would have felt if I'd left them alone.
In a nutshell, does utilitarianism state that I am morally obliged to curb my selfish desires so that other people can be happy?