Resources on left-wing ethics/morality?

If by 'communism' you specifically mean some brand of dialectical materialism or it's offshoots, then you will have to start with the OGs.

I would consider reading the 'Anti-Durhing' by Frederick Engels. Engels essentially posits what a communist ethics may look like by equivocally stating what it is not.

However, as a materialist who is basing himself off of a reversal, though not exactly contradiction of, Hegel (though not a vulgar materialist as future people would portray them), Engels posits that what a communist ethics will look like will likely be intimately related to the material conditions that give rise to it. The idea though is to pursue the emancipation of the working class, which likely means that you believe in things like human dignity, that humans are not born evil or good, and most importantly, that the freedom and rights of the individual are not contradictory to the freedom and rights of the group.

Ultimately, both Marx and Engels did not take theoretical ethical postulates very seriously, nor believed in a purely virtue, care, deontological or consequentialist (particularly they were against ideas of utilitarianism) model of ethics. And this is because communism isn't an ideology, it is the movement through history that allows the working class to free itself from bondage. However you don't pursue that freedom necessarily because it will grant the maximum amount of happiness, you pursue it because freedom is what allows humans to pursue virtue. Just because no one is hungry doesn't mean that you can't be charitable, in fact, because no one is hungry making the choice to prepare a personal dish for someone can mean even more because there are no actual physical consequences for not doing so.

For Marx and Engels though, the biggest reason you pursue communism is that the alternative is, and has to be, due to the material conditions and internal contradictions created by capitalism, barbarism, a stifling of human choice, freedom and thus virtue. And we, collectively, as a society in the US, are choosing barbarism and actively applying it to over-exploited countries.

In this same line of thinking, as Marx himself states, if there is to be an ethical maxim for communists, it is 'From each according to their ability, to each according to their need.' How exactly you want to apply that to your life, is up to you. You get to make the specifics of those definitions, and hopefully, someday, the material conditions will cause enough people to agree with you on those specifics.

The closest thing I can think of is probably the works of bell hooks like The Will to Change for men, but generally speaking it's a little outside of the well travelled path. Most questions of individual behavior are kinda gonna automatically be answered by doing a materialist analysis of collective action and social relations (e.g. do you want to work for an oil business? consider the place it occupied within the structure that produces climate collapse, that kind of thing).

Honestly not even communists know what a communist should do and not do in every possible situation.

If I understand correctly your difficulty is finding the courage to do more as a communist?

Community helps a lot on this, having other people do things you're afraid to do yourself can give you the confidence to take more steps. Also learning from communist history can help, by finding inspiration in people that fought either literally, or by doing organizing work, or by protesting, people staying strong while being jailed and punished for their beliefs. Learning from example from the smallest to the biggest actions can give you the strength to do a little more, even if it's a little.