You are stuck in the middle priesthood. It died. The one that matters is the eternal, which received tithes before and after the middle priesthood. The mortal high priest of the second priesthood received the last of the tithes as prescribed by the law, while the eternal priesthood before and after, which was always all along in effect, receives tithes of all our substance, as Melchizedek did of Abram. Abram volunteered the tithe, not under commandment. The old covenant didn't require that, but accepted a token of their substance.
By the way, only people who die can tithe.
Required to "tithe"? No, but we are to support the church minister "even so", likewise, no less than. It's a commandment, ordained of the Lord (see last post). So it is the church can rightly promote tithes and offerings. Under the new covenant those who have no part in that, nor assemble together with believers, as has been well established throughout the history of the church, have no part in blessing of the tithe. The only promised blessing of "offerings" is essentially a repayment in kind, the little giver reaping little.
So all Christians have a choice. Take part and prosper by the hand of the Lord, or go dig it out on your own. Even the unbeliever can plant a seed and get a crop, but can't get God's ear when wanting it blessed. Neither can a stingy Christian benefit.
Christ is indeed the end of the law for those who believe in him. Believing is doing his commandments, which also issued from the apostles. It isn't enough to say you believe but don't obey, so the devils believe and tremble. Unbelievers remain under the law which is still in existence for the ungodly.
The truth is still hidden from unbelievers. It can't be fathomed with the natural mind.