When I come (erchomenos). Present middle participle of erchomai with the time of the future middle indicative eleusomai (coming I shall come).
In the fulness of the blessing of Christ (en plērōmati eulogias Christou). On plērōmati, see Rom 11:12. Paul had already (Rom 1:11.) said that he had a charisma pneumatikon (spiritual blessing) for Rome. He did bring that to them.