Blessed (μακαριο). See on Matthew 5:3.

Are forgiven (αφεθησαν). First aorist passive indicative of αφιημ, without augment (αφειθησαν, regular form). Paul quotes Psalm 32:1 and as from David. Paul thus confirms his interpretation of Genesis 15:6.

Iniquities (ανομια). Violations of law whereas αμαρτια (sins) include all kinds.

Are covered (επεκαλυφθησαν). First aorist passive of επικαλυπτω, old verb, to cover over (upon, επ) as a shroud. Only here in N.T.