Is it based on the pre-Mosaic method? I see Abraham tithe once, of the spoils of war, and then give the other 90% back to the king of Sodom. Where did Jacob give his tithes? How do we relate that to the church?
Tithing does precede the Mosaic Law. Starting with the first book of the Bible—Genesis--we can see an indication of what God has in mind for His people about tithing long before the giving of the Law upon Mt. Sinai.
Similarly to the actions of Cain and Abel the tithe of Jacob would have been offered up as some sort of sacrifice. There is no place in Scripture where we can point to explicit commands of tithing pre-Law. That said, as we read Genesis we cannot account for what is there, unless, we are willing to presuppose a previous revelation by God.
This relates to the church rather easily. It is being willing and able to not only be obedient to God but to be faithful as well. Teaching or affirming spontaneous giving has never been God’s primary means of giving, at least in any offering given to Him. In fact, Cain is an excellent example of God’s dealing with man in a way involving some sacrifice.
The tithe law that we first see in Leviticus is difficult for me too. Resources I've looked at show that they actually tithed up to 23% between three different tithes. That tithe seemed to go to the Levites, who then gave a tithe to the priests (so priest received 1% of the total tithe).
Much of the system that exhausted the other tithes related to a system of sacrifices and something prescriptively given in the Mosaic Law. The tithe in any either case is a tenth. Its distribution remains myriad to this day, at least in some part. How many pastors use tithing money to pay for some need or want in the church itself? Some pastor’s use their own tithes to finance other staff in the church.
Are Pastor's the New Testament equivalent to the Old Testament priests? In the Old Testament only the Priest could do the ministry - how does that come into play with the New Testament concept of the priesthood of all believers? Can a Pastor claim 10% or 1% of tithes as his?
No. Symbolism does not equate to sameness. I would say 10% is the only proportioned giving in the text of Scripture.
Is it Biblical for Pastor's to be the wealthiest member in the church - receiving tithes? Is it Biblical for ministry to tell parishioners that it's God's money, and they have no say once they pay it - even when ministry spends much on overhead, and little on the poor which was so important to God in both Testaments? I am a Pastor by the way - just asking some tough questions : )
I do not think the Scriptures actually discussed the issue that specifically. I do think humans can abuse any system or structure. The children of Israel demonstrated this and yet God loved them. Thankfully He still loves us. I do think that certain levels or degrees of accountability are always applicable. Some churches give financial reports monthly. There are also certain advisory boards or collection of elders we can use to help guide most expenses of the church.
Jesus mentions that the tithe shouldn't have gone undone in the New Testament verses, but who were they tithing to? It was still Old Testament tithes to the temple.
I don’t think New Testament believers are accountable to the rigid nature of the Law, but are accountable to a greater Law, indeed written on the tables of our heart.
I definitely see where the New Testament makes provision for preachers to receive compensation (though Paul didn't seem to take more than his basic needs on occasion and still worked), but still looking for more information I guess.
1 Corinthians 9:13-14: Don’t you know that those who serve in the temple eat food from the temple, and those who serve at the altar receive a part of the offerings? (14) In the same way the Lord commanded those who proclaim the gospel to receive their living by the gospel. NET
I think this is where Paul clarifies some system of giving for New Testament believers. The beginning of vs. 14 starts with a form of καί that lets us know that the prior principle—those who serve at the altar receive a part of the offerings—is still applicable in some sense. Since the Mosaic Law was fulfilled the reference here could be to the transcovenantal principle of giving a tenth, the first of our fruits—regardless if it be money or commodity—to their local pastor.