How much does God love us? He gave us everything. He made everything and then told us to look after it. He saw how lovely, how intricate all of creation was and then decided to make us, that we, of all creatures, would complete it. And after millennia of us collectively and consistently messing up, He still loves us most.
God presents Himself to us daily in different ways but always in love. It could be hearing a song that you like and haven't heard in a while or standing a long time in a checkout line because if you left sooner, you'd be in a wreck or someone giving you a compliment when you really needed to hear it. All of these are examples of acts of love from God, whether we recognize it or not.
Through the salvation He offers, He makes up for our shortcomings. His endless grace completes what we lack in keeping the law. We don't have to worry about not living up to the law because we have Jesus. Thus we are free from it because Jesus is our salvation, not the law, and we are no longer bound by what it says as we are freed by what Jesus has done for us and by what He tells us. Paul says the law condemns, but those of us who have accepted Jesus know that He does not condemn, He saves (John 3:17).
Paul says his love for Onesimus is vast and proves it by doing what Jesus did for us: took his place and his debt. "So if you consider me your partner, welcome him as you would welcome me. If he has wronged you in any way, or owes you anything, charge that to my account" (vs. 17-18, NRSV). It's very least-of-these, isn't it? This is Paul directly following Jesus in standing with and loving the marginalized. This is Paul loving his fellow man as Jesus loves him.