It wouldn't matter if Trump were running against the Antichrist.
Now, to determine whether it's licit to vote for Trump, one can apply double effect

The bolded shows you are misunderstanding double effect as it applies to voting. Of course it would matter if Trump were running against the Antichrist, and 99% of Catholics and the trad clergy know that and would tell you. But you think you know better than them, so ...
Let's begin. Let's start with the example of double effect you agreed with on the other thread, that of killing a terrorist while minimizing civilian deaths/collateral damage. The bolded is like saying, "of course I can kill a terrorist if I want to. It doesn't matter if one person dies near him, OR ONE MILLION PEOPLE DIE". That's zionist israel's reasoning and its as false as the above. Of course the number of people that die matter because that is factored into the "proportionality condition" of double effect. Let's recap double effect.
Double effect: "This set of criteria states that, if an action has foreseeable harmful effects that are practically inseparable from the good effect, it is justifiable if the following are true:
- the nature of the act is itself good, or at least morally neutral;
- the agent intends the good effect and does not intend the bad effect, either as a means to the good or as an end in itself;
- the good effect outweighs the bad effect in circuмstances sufficiently grave to justify causing the bad effect and the agent exercises due diligence to minimize the harm.[2]"
Since, as even you agreed on another thread, the good of gaining a pro life victory would sufficiently outweigh the effect of even an otherwise pro life candidate being for birth control, it clearly follows the good of supporting a moderately pro-life platform like Trump-Vance outweighs "the Antichrist" and the same applies to hαɾɾιs' pro-abort platform. I agree with you double effect is the operative principle. One doesn't need any other principle.