Sure, there are times what is good and needed in a given moment is a mystery. But more often than not we know. It's just not always what we want. We don't need a handbook to know how to treat others with kindness and dignity, taking into account their needs and interests, taking into account that they need and want the same basic things we need and want. Love your neighbor as yourself is not a mystery most of the time. If someone wants to justify some horrendous act by saying it was love, that's on them and we usually can tell it's off. The only real mystery is why we wouldn't live in love from the get-go.
Well my objection is not that love suffers from epistemic limitations. Of course it does, but no more than anything else.
So again, the claim is that love is not substantive and sufficient in itself without an adequate notion of the good. In this post you include various notions of the good, such as the idea that others want the same things we want and that they should get what they want, or that they should not be harmed, or that they should not be coerced, etc. But if someone does not agree with you about what is good then they could love while, say, harming. Love in itself is a very thin notion that is primarily about one's intention. In a society where the good is commonly agreed upon we can use the word without thinking about it, but that is because we have a shared notion of the good, and this is not always true.
If one lives by love it will prohibit behaviors that are not loving. [...]. Love causes no harm (pace Paul), and when able to act in a non-paternalistic way (again Paul -love is not forceful), love contributes to the good of others. That covers the whole territory, even the gaps left by the set of rules, if faithfully lived out.
Again, I don't think it will definitively exclude hardly any behaviors. For example, you say that "love causes no harm" (which is a rule, by the way: a roundabout way of saying 'do not harm'). Yet when faced with the Trolley Problem you have claimed that murder is sometimes morally
necessary. There can be no doubt that murder is harmful, and yet you defended your position on the basis of love.
Now it may seem strange to hear someone say that sometimes to be loving means to be a murderer, but
I don't find it strange at all. When people talk about what is "loving" they are generally just talking about what they think is best, and in your case you see consequentialism as best or most loving, which includes justifiable murder. In the end these moralities based on "love" seem to be quite flimsy, and they don't seem to be any different from any other morality. I don't see any difference between a consequentialist and a love-consequentialist (and maybe the "love morality" is just a fancy way of dressing up intuitionist consequentialism).
The problem with the idea that a set of rules can function as a backstop is that not every situation fits the rules. Most probably do, but certainly not all. [...] When the Nazi knocks on the door, you lie or whatever; you don't keep the truth-telling rule since a much greater good is at stake. But, yeah, it takes attention and true concern for others, which rules or backstops also can't provide.
Well this is a big topic, but you are essentially saying that sometimes rules are inapplicable and therefore we should focus on love. I like the Aristotelian approach. According to Aristotle prudence is required to apply the various rules, and the guiding principle is primarily justice, not love. The basic problem is that rules are never dispensed with. In the Nazi example you are merely substituting a rule against murder (or cooperating with murder) for a rule against lying, and claiming that the murder rule takes precedence. That's fine, but the operative principle is prudence in knowing how to apply the correct rule and knowing the hierarchy of rules. It's not an anti-rule approach.