Are forgiven (aphethēsan). First aorist passive indicative of aphiēmi, without augment (apheithēsan, regular form). Paul quotes Psa 32:1. and as from David. Paul thus confirms his interpretation of Gen 15:6.
Iniquities (anomiai). Violations of law whereas hamartiai (sins) include all kinds.
Are covered (epekaluphthēsan). First aorist passive of epikaluptō, old verb, to cover over (upon, epi) as a shroud. Only here in N.T.