Notice three things in Romans 8:35.
1. Christ is loving us now.
A wife might say of her deceased husband: Nothing will separate me from his love. She might mean that the memory of his love will be sweet and powerful all her life. But that is not what Paul means here.
In Romans 8:34 it says plainly, "Christ Jesus is the one who died, more than that, who was raised, who is at the right hand of God, who indeed is interceding for us." The reason Paul can say that nothing will separate us from the love of Christ is because Christ is alive and is still loving us now.
He is at the right hand of God and is therefore ruling for us. And he is interceding for us, which means he is seeing to it that his finished work of redemption does in fact save us hour by hour and bring us safe to eternal joy. His love is not a memory. It is a moment-by-moment action by the omnipotent, living Son of God, to bring us to everlasting joy.
2. This love of Christ is effective in protecting us from separation, and therefore is not a universal love for all, but a particular love for his people, those who, according to Romans 8:28, love God and are called according to his purpose.
This is the love of Ephesians 5:25, "Husbands love your wives as Christ loved the church and gave himself for her." It is Christ’s love for the church, his bride. Christ has a love for all, and he has a special, saving, preserving love for his bride. You know you are part of that bride if you trust Christ. Anyone, no exceptions, anyone who trusts Christ can say, I am part of his bride, his church, his called and chosen ones, the ones who verse 35 says are kept and protected forever no matter what.
3. This omnipotent, effective, protecting love does not spare us from calamities in this life, but brings us safe to everlasting joy with God.
Death will happen to us, but it will not separate us. So when Paul says in verse 35 that the "sword" will not separate us from the love of Christ, he means: even if we are killed we are not separated from the love of Christ.
So the sum of the matter in verse 35 is this: Jesus Christ is mightily loving his people with omnipotent, moment-by-moment love that does not always rescue us from calamity but preserves us for everlasting joy in his presence even through suffering and death.