Was tithing 10% required or encouraged by the early church?

Is simple impossible that the original church established by Jesus and Apostles have requested Tithing to it's members. Why? Very Simple.

The Levites Where a Life and in exercise of their functions under the law of Moses in those early days!

So asking for tithing will have been to violate their rights. The original members were also Jews.

This is why the church only asked for donations. But the real missionaries like Paul, worked with their own hands to provide for himself. Remember the one in Salarie, do not worry about the sheep but their salary.

Tithing is not a Christian teaching, Christ never taught it even though there are instances where He could have. The apostles never taught it! It is an Old Testament teaching which the church has and is still using to produce money. Tithing is under the law, we are not under the law but under grace. Read Hebrews chapters 7-9 and you will see that we are not in the Levitical times or have a priest. Jesus is from the tribe of Judah which did not participate in that law.

There were a couple of instances where Jesus could have taught tithing. The first was when He was in the temple and watching the offering, He said the woman who gave her all (which was two mites), gave more than all of them because they gave of their abundance; now, if it was about tithing then if the woman would have given just one mite she still would have given more because it would have been a 50% tithe. Second, when the rich man said he had done all and Jesus said one that you are lacking is to sell all that you have and give to the poor and you will have riches in the kingdom -- notice that Jesus didn't say sell all that you have give the 10% tithes and the rest to the poor, He said give it all and you will have riches in heaven. This is not for Christians because there were no Christians at that time!

Here Jesus confirm the tithe in the NT:

Matthew 23:23 KJV
Woe unto you, scribes and Pharisees, hypocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier matters of the law, judgment, mercy, and faith: these ought ye to have done, and not to leave the other undone.

And here, author of Hebrews explains whom receives that tithe:

Hebrews 7:8 KJV
And here men that die receive tithes; but there he receiveth them, of whom it is witnessed that he liveth.

Another aspect is, in the Melchizedek era, before the law, Abraham gave the tithe Melchizedek, impling that that "rule" is transcending from laws.

Giving everything (or even 10%) is an evangelical counsel: it's not required for salvation. As you quote, the early Church only directed its members to give what they could, not a minimum amount (much less everything). Paul even writes, just before the passage you quote, in 2 Corinthians 5:5:

So I thought it necessary to encourage the brothers to go on ahead to you and arrange in advance for your promised gift, so that in this way it might be ready as a bountiful gift and not as an exaction.

And while I'm no Biblical scholar, Matthew 19:21 ought to be read in context. Just preceding this verse is Matthew 19:16-17:

¹⁶Now someone approached him and said, “Teacher, what good must I do to gain eternal life?”
¹⁷ He answered him, “Why do you ask me about the good? There is only One who is good. If you wish to enter into life, keep the commandments.”

That's it: the only thing required for salvation is to keep God's commandments, which Jesus enumerates in Matthew 19:18-19: poverty or charity is not listed among them.

Then taking the verses after and including Matthew 19:21:

²¹Jesus said to him, “If you wish to be perfect, go, sell what you have and give to [the] poor, and you will have treasure in heaven. Then come, follow me.”
²²When the young man heard this statement, he went away sad, for he had many possessions.
²³Then Jesus said to his disciples, “Amen, I say to you, it will be hard for one who is rich to enter the kingdom of heaven.
²⁴Again I say to you, it is easier for a camel to pass through the eye of a needle than for one who is rich to enter the kingdom of God.”
²⁵When the disciples heard this, they were greatly astonished and said, “Who then can be saved?”
²⁶Jesus looked at them and said, “For human beings this is impossible, but for God all things are possible.”

Jesus is saying in verse 21 that if you wish to be perfect, you ought to sell everything and give to the poor, but the verses that proceed from verse 21 explain how impossible that is for people without God.

The disciples' astonishment and query to Jesus in verse 25 speaks to this, essentially saying, "whoa, nobody's going to do that: does this mean nobody will be saved?" Jesus in verse 26 then specifically states that God will save human beings by performing the impossible task: saving those who couldn't normally be saved because they aren't perfect.

Or as the New American Bible explains:

Riches are an obstacle to entering the kingdom that cannot be overcome by human power. The comparison with the impossibility of a camel’s passing through the eye of a needle should not be mitigated by such suppositions as that the eye of a needle means a low or narrow gate.

Beyond that, the Didache, an early Christian writing that dates to around the same time as Paul, mentions one of the ways you could tell a false Apostle from a real one:

Let every apostle that comes to you be received as the Lord. But he shall not remain except one day; but if there be need, also the next; but if he remain three days, he is a false prophet. And when the apostle goes away, let him take nothing but bread until he lodges; but if he ask money, he is a false prophet.

It wasn't until much later that justifications for tithing were formulated: the Catholic Encyclopedia mentions the first serious attempts to tithe dated to around 567 CE and 585 CE with the Councils of Tours and the Maçon, respectively.