[рони]

Malleys,
может один цикл?

addEventListener("input", function(event) {
	const form = event.target.closest("#my-form");
	if(!form) return;
    let sum = 0;
    for (const {value} of form.querySelectorAll("input:checked")) sum += Number(value);
	form.querySelector("output.summa").textContent = sum;
});