I accept the man called Jesus as being a follower of Judaism. I believe him to have been a teacher of Reformed Judaism.
First off, I really appreciate your thoughtful post. Thank you.
Jesus certainly praMarcticed Second Temple Judaism. I am convinced that he was a Pharisee (see his acceptance of the Prophets and belief in the Resurrection). However, he was of the school Hillel (a more lenient interpretation of law) rather than school of Shammai (a very strict interpretation of law that dominated the Sanhedrin during Jesus ministry years).
The four movements of Judaism that we have today (Orthodox, Conservative, Reform, and Reconstruction) didn't exist in Jesus' day. The first of these to come into existence was Orthodox Judaism, which traces back to the publication of the Shulchan Aruch which for the first time in Judaism promoted the idea that Jewish law is now carved in stone and cannot be changed. That happened in 1563 CE. Reform Judaism didn't start evolving until the 19th century.
Reform Judaism is complex, but I would like to say two things about it. First, it views halakha (Jewish law) as changeable. Second, it sees obedience to the law as voluntary. I don't see how anyone can say that Jesus viewed keeping the law as a voluntary thing. Let's look at just a few passages:
Mark 10
17 As Jesus started on his way, a man ran up to him and fell on his knees before him. “Good teacher,” he asked, “what must I do to inherit eternal life?”
18 “Why do you call me good?” Jesus answered. “No one is good—except God alone. 19 You know the commandments: ‘You shall not murder, you shall not commit adultery, you shall not steal, you shall not give false testimony, you shall not defraud, honor your father and mother.
So basically in that passage, Jesus connects eternal life to keeping the commandments. That doesn't sound much like obedience is voluntary. Let's go on.
Matthew 5
17 “Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. 18 For truly I tell you, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. 19 Therefore anyone who sets aside one of the least of these commands and teaches others accordingly will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven. 20 For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven.
So here we basically have two points:
1. That the Law is still in force "until heaven and earth pass away."
2. That even keeping the very least of these laws is incumbent on Jews.
Again, doesn't sound much like obedience is voluntary.
But it goes even farther than that. In Matthew 23, Jesus even supports keeping the Oral Torah in addition to the written Torah (very much a Pharisaical teaching).
Matthew 23
1 Then Jesus said to the crowds and to his disciples:
2 “The teachers of the law and the Pharisees sit in Moses’ seat.
3 So you must be careful to do everything they tell you.
"Everything" they tell you means Oral Law as well as written. Jesus is clearly asking this of his followers. And it doesn't appear to be voluntary.
Later in the same chapter, Jesus addresses the Spice Tax, which is Oral Torah. He says to the Pharisees:
Matthew 23
23 “Woe to you, teachers of the law and Pharisees, you hypocrites! You give a tenth of your spices—mint, dill and cumin. But you have neglected the more important matters of the law—justice, mercy and faithfulness. You should have practiced the latter, without neglecting the former.
IOW, he tells the Pharisees to obey the written Torah (justice, mercy, faithfulness) BUT ALSO keep the Oral Torah ("the latter" meaning the spice tax).
So it is clear that not only does Jesus teach obedience to the law, but he includes in that the Oral Torah.