in Whom we have redemption [the relative pronoun refers back to that loved Son, the source of redemption]
through His blood [the means whereby that redemption is even possible]
the forgiveness of sins [this noun phrase just sits there at the end of the string of thought not tied by a relative pronoun to anything]
"In whom" - it is only in the Beloved Son, in Christ, in Him that we have redemption. There is no other way. Not one. This is the way that God has chosen. For a deeper look, check out the Gems I wrote on Romans (#151 – 158 – The Gospel in a Nutshell – another single Greek sentence). These concepts are covered comprehensively by Paul in the book of Romans.
Notice the tense of "we have redemption". It is a present tense reality. In Christ we have redemption now, but it will reach its fulfillment at a time yet to come. The word for redemption signifies deliverance from sin and from the consequences of sin; from the power, guilt, and legal consequences of sin. The atonement has been made by the Lord Jesus Christ, paid through his blood – the means whereby such atonement has achieved. The resultant redemption is for all the chosen ones; not angels, but men. Not all men, but elect men, those chosen in Christ, predestined to be adopted as His children by Him. The price has been paid by Christ to make us right before Father God. That is what redemption is all about.
We are not to suppose that this is all the benefit which we receive from his death, or that this is all that constitutes redemption. It is the main, and perhaps the most important thing. But we also obtain the hope of heaven, the influence and presence of the Holy Spirit, grace to guide us and to support us in trial, peace in death, and many more benefits. This is what is tumbling out of Paul as he strings together all this thoughts. These are the spiritual blessings. Still “forgiveness” is so prominent and important, that the apostle has mentioned that as if it were all.
Examine the connection of this phrase - The forgiveness of sins - we obtain through his blood, or through the atonement which he has made, the forgiveness of sins. But I have just realized in doing this live quiet time and checking out Ephesians deeper than I have ever done before, that the segment "the forgiveness of sins" is hanging without a referrant. Paul connects everything in this long sequence; all of it is tied in to something else. It all unfolds in a related connected whole. Except when it comes to "the forgiveness of sins". It is not directly connected with what goes before it by a relative pronoun, or logical conjunction or any linked reference at all. What follows, according to (because of) the riches of His grace, is linked back to the blessings that flow from His grace. But forgiveness of sins just sits there seemingly unconnected. It doesn't seem to relate to what is immediately before it - through His blood. Yet it could do. The thoughts could be connected in that way. I.e. . . . in whom we have redemption. Through His blood the forgiveness of sins because of the riches of His grace. Or it could be a noun phrase in apposition related to "redemption. That is, one of the benefits or redemption being forgiveness as I said above.
It is a complicated section and one which requires more thought. Look at the way the versions handle this and see if that satisfies you. I will continue to dig on it and see if I can solve the issue of where is connects. But I don't expect you to stay with me on this. If you are interested at all then at least I have raised the issue with you and you can look further if you wish. I will do that but I won't bore you with the details. If you want the details then do some of you own work and then talk to me about it at a later date. We will compare notes.
My last parting shot for the day: note the plural use of "sins". Paul does not say "sin" - the concept or the principle of sin. He says "sins": of all sins, original and actual, past, present, and to come. This forgiveness is all encompassing but only available in Christ. Christ's once for all act covered all sins ever committed by anyone for all time. Wow, take that one in and chew on it. Enough for today.
Doubt wonders, "Have I done enough to go to heaven?" Grace answers, "No, you haven't. But Jesus has on your behalf." Max Lucado
It's all about Jesus – first and last, beginning to end. There is no other solution. Jesus IS the answer to everything. God thought of it; it's His solution. Just accept it and say thanks.