copias eius, maiestatem dominatus
must be "his troops, the greatness of his rule". "his abundant rule of greatness" is not a possibility because copias
does not mean "abundant" but abundances or troops, "greatness" (maiestatem
) is not genitive so it cannot be "of greatness", and dominatus
could not be the direct object unless plural which does not make much sense based on its meaning.
negaretque quemquam umquam beatiorem fuisse
"deny" is too defensive a word in English. It is usually better to translate as "said not", as in "and he said
anyone had ever been more fortunate".
is better translated "to experience" in this case. It is also deponent so it could never mean "to be tested" in a passive voice.
is a superlative. I would say "a most exquisite dinner".
Other than that and elduce's comment, it looks good. You stayed away from literal translations in some of the parts which could sound odd in English, which is a good thing and opens the door to more stylistic translations.
flebile nescio quid queritur lyra, flebile lingua murmurat exanimis, respondent flebile ripae