I'll tell you what I believe about your situation and what I read in the Bible about it.... but you probably don't want to hear any of it. I'll try and break down my answer to address the various questions/ points that you bring up....
1) I do not believe that a lack of sexual interaction is a form of unfaithfulness. A lack of sexual interaction can occur for various reasons-- biological, emotional, psychological, etc. Even if the cause is a spouse who is withholding sex out of malice, I believe that the spouse is sinning but still not unfaithful. If one spouse is withholding sex it usually stems from other problems in the marriage-- in other words, the issue is not sex, it is something else. That is not unfaithfulness nor infidelity. The lack of sex is just the symptom of a different problem.
2) Your union in marriage was legit. It doesn't mater who performed the ceremony (civil vs. traditional church), and it doesn't matter if one spouse is a non-believer. Two people entered into a covenant together and promised themselves into the unity of marriage. Neither of you was forced into marriage. It was a choice that two of you made. You joined flesh as one and lived in a marital relationship for many years. The Bible never says that if one partner is not a believer than the marriage is null under God's eyes. Nor does the Bible say that if the ceremony was performed in a civil manner rather than using God's name, then it is null. The fact is that the two of you are/ were married and it is a legitimate marriage under God.
What the Bible does say about a believer and non-believer union is that if the non-believer wants out of the marriage then the believer should let them go, but if the non-believer is willing to stay then the believer should stay. Read
1 Corinthians 7: 10-16.
Many years ago you committed yourself in marriage to another person. Even if you were the biggest atheist around, the marriage would still be valid in God's eyes.
3) You are married, and I will tell you that you most likely did not hear God tell you that there is someone else who will come into your life. What you heard is your own desire speaking. The Bible is also clear about re-marriage following a divorce. Look again at
1 Corinthians 7: 10-11..... if one spouse is a non-believer (and the other a believer) and the two separate (or divorce) then they should not remarry or else they should be reconciled back together. Look over at
Matthew 19, particularly verse 9.... if a man (or woman) divorces for any reason other than marital unfaithfulness then they are not permitted to remarry or else it is adultery.
Which is why you are trying to justify the lack of sex in your relationship as unfaithfulness, right?
Look also at
Matthew 5:31-32...again, if it is for any reason other than marital unfaithfulness then remarriage would be adultery.
This is why I do not believe that God is telling you that he has someone else out there for you. I don't believe that God would contradict himself or his word. God is not going to tell someone who is married that there is someone else in store for them. (And normally I am not so blunt nor bold as to flat out tell someone that it isn't God they are hearing.)
Again, the lack of sex in a marital relationship is not unfaithfulness... it is a symptom of some other problem. Unless it is specifically due to the other party's infidelity, then it is not unfaithfulness. And infidelity can be quite broad..... Infidelity is not just limited to sexual relations with another.
I believe that you know the truth, and you have read the Bible, and you are just looking for loopholes. You said yourself that you do not want prayer for restoration. You are as the Bible describes.... one who has hardened his heart. That is why God has made some provisions for divorce-- because man has hardened his heart (and woman).
Malachi 2:15-16 God says that he hates divorce.
Matthew 9:8... God permitted divorce because Man had hardened his heart.
Divorce is something that no one should ever have to go through. I am sorry that you are having problems in your marriage, and have been having problems for a long time. I am sorry that you are hurting and angry. I am sorry that you feel that you can no longer be in the marriage. It sounds as though in your heart you have already divorced from your spouse and now you are seeking support and justification for it. How does your spouse feel about it all? Does your spouse want reconciliation?