God had given us a commandment the Tithes & Offerings. How people today followed the commandment?

Understood.

However, if you were referring to Jacob vowing to give the tenth to God that is in Genesis 28:22. He never received the land, so his descendants who did receive it were required to fulfill his vow. That's not stated explicitly in scripture, but there it is and it's as good as any explanation for the existence of tithes.[/QUOTE]
I agree: it's not stated in Scripture. I leave it there and don't make more of it than that.

Unto each person will be according to the measure of their faith

This was a requirement for the Hebrew people at a time when there was a temple and levitical priests, meant for sin sacrifices, food offerings to God, to supply food for feasts, to support widows, etc.

There is no carry-over to gentile believers.

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Our Lord Jesus fulfilled the Law in Tithes & Offerings.
MARK 5:17
17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.

Because The Law in Tithes & Offerings must be fulfilled in any generation.
ECCLESTIASTES 1:9
9 The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun.

God The Father never change his Law in Tithes & Offerings.
MALACHI 3:6
6 For I am the Lord, I change not; therefore ye sons of Jacob are not consumed.

But The Law in Tithes & Offerings is Spiritual. According to Paul
ROMANS 7:14
14 For we know that the law is spiritual: but I am carnal, sold under sin.

The Spiritual Law is never seen. According to Paul
2CORINTHIANS 4:18
18 While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal.

Therefore Jesus fulfilled the Law (Matthew 5:17) in Tithes & Offerings Spiritually and can't be seen.
That is why we never read that Jesus Followed the Law in Tithes & Offerings same as the people fulfilling it today.

The Law of Tithes & Offerings fulfilled of Jesus is from God Revelation (Spiritual or Can't be seen)
While the Fulfilment of The Law in Tithes & Offerings as people followed today is from Man's explanation in God's words (Literal in meaning).

We pay a tithe of 10% to our local church, from my husband's salary and my investments. We also help out with local ministries and good charities, as we are able.
Then your church isn't doing enough. It should be trying to convert heathens and running outreach ministries. I am not trying to boast, but we give a lot more than $900, because it's Biblical, we can afford it, and we know it's put to good use.

Missions should ALWAYS be under the authority of a specific local church. And if your church isn't correctly disbursing funds you need to have a meeting of elders.

As far as it being a custom for Israel only: I'm sympathetic and not with this, because I'm a quasi-theonomist but also a particularist. My view is that 10% is commanded, but that is no longer the duty of the state to enforce it. If you don't pay tithes without good reason you should be disciplined by the church.

Echoes of the Israelites who wanted a king rather than to be ruled by God. Now pastor-kings and their bootlickers bear rule over the sheep like the world does, and God still hates it

When you find Paul’s missing letter in which he states that paying tithes to the local church is required, you will have a sound case. In the meantime, your position is without scriptural foundation.

You'll find Reformed Christians believe in a much stronger analogical application of the old testament than most Evangelicals. It does not have to be in the New Testament to apply to the church.

Also scriptural evidence that the tithe was an income tax or even money would be good