You can claim that all you like but what you have provided in not compelling at all. In my profession, I evaluate evidence all the time and your evidence doesn't even get out of the starting gate.
I will further posit, in your apparent rejection of Jewish law, you must hope to be under the moral authority of the holy catholic apostolic church, for if you reject the Jewish tradition you must take the catholic, else you are orphaned with no line of inheritance to the scriptures, trusted to the Jews and holy catholic apostolic church for transmission.
I'm not even sure where to start with all the faulty assumptions in that paragraph. As a Protestant, I hold to the Word of God as contained in the Old and New Testaments.
Rejecting Jewish law? Not being convinced by an irrelevant passage from the Old Testament isn't rejecting Jewish law. Nor is rejecting the writing of some person who claims to be an expert in Jewish law who you chose to cite. Particularly, when his commentary didn't even get to the issue at hand. Nor is rejecting your interpretation of Jewish law a rejection of Jewish law. Nor is not accepting your reading of your interpretation of Jewish law into Paul's writing.
Are you really claiming canonized Scripture as a Catholic exclusive? The process of canonization took place long before the Protestant Reformation. Back at a point of common heritage for both the Catholics and the Protestants. When a tree forks, neither fork has a superior claim to the trunk. Protestants can trace their lineage back to the apostolic church as well and prior to the 1500s, it would be a shared heritage. What you just presented is a false dilemma.
Your argument has Jesus breaking the commandment in such a way to apostasize the siblings you assert he has, rather than fulfilling their Torah obligation to care for a widow, which is preposterous in its cultural bias, even if the Gentiles behave thusly.
In your legalistic view, there seems to be only way in which Mary could be cared for by her children (if they existed): living in their households. What if Jesus, his siblings, Mary, and John all agreed that the best provision for Mary was to go to John's household? Have they not provided for their mother (which is Paul's point)? What if the other siblings were paying for Mary's support while she lived in John's house? Would that not be providing for their mother? We know nothing about the arrangements except that Mary was to live with John.
The problem with your scenario is that those who conjecture that Mary had other children reject the testimonies of the Reformers themselves, who, as others have already demonstrated, defended the teaching of the holy catholic apostolic church that Mary had no other physical children save Jesus. Thus the burden of proof is on the modernists who originated the supposition that Jesus had other siblings through Mary.