This is where you err. The church teaching is that each act of intercourse must be ordered to both unity and procreation, a completed act.
There is a point of no return where you should not thwart the natural orientation of the act. But if things do not work, they do not work. And the unitive aspect of sex is not exclusively found in coitus, only the procreative aspect is exclusively found there.
Nope, the Church is very clear on this subject. There is no harm in a couple intending to have intercourse and being unable to finish due to ED or premature ejaculation or painful intercourse. They can of course stop.
You’re omitting the problem of delayed ejaculation where the man is incapable of reaching a climax in time to not hurt his wife through intercourse.
But we may NOT replace intercourse with other sexual acts to climax. That is, by definition, disordered use of our sexual faculties.
Okay, so sexual sins are a part of the commandments ordered to loving your neighbor as yourself. Any moral question that does not include a question of what love (caritas/agape) demands of us is
NOT a moral question at all. So the question here is about the what demeans that love.
If a man tells his wife “Hon, I’m super tempted to masturbate,” and she engages in it in a disengaged manner because she can’t get into it, he is masturbating
regardless of the fact that they’re engaged in coitus. There is nothing loving or mutual in simply using your spouse as a tool to get off. In fact, he’d have more dignity not to bother her at all but to simply confess his lack of chastity in that he masturbated. No more spiritual pride at convincing himself he didn’t masturbate.
Loving sex is one that afterward leaves the couple feeling happy and connected. The cuddle time afterward is where you see the immediate fruits of it: the affection, the vulnerability, the smiles, the laughter. Beyond that, there is the moral component over whether it’s prudent to have sex. And lust will always be challenged when prudence tells us we must deny ourselves. Lust is not the desire for disordered actions but the inability to control ourselves.
Not being able to have intercourse but expressing your love other ways as best you are able to is
not lustful. It is
loving.
And no, you’re not going to get this from Aquinas as Aquinas did not acknowledge that sex as having a purpose other than procreation. We’re talking about arranged unhealthy marriages where marriage was thought of as a lesser state to temper your lust. Today, we say that all, even the married, are called to chastity.