I am always confused why people call the Queen and the Royals scroungers. The Queen and the Royals receive a small percentage of the proceeds of the Crown Estate - properties they surrendered control over under George III and agreed to by each monarch (previously, there proceeds were administered by the monarch and the proceeds were used to fund the government). This estate is worth 8.1 BILLION and the proceeds principally go to the government. If the monarchy were to be abolished, they could rightly claim back their properties and would be much, much better off than they currently are. So no, the taxpayer does not fund the monarchy in reality. The government actually earns quite a pretty penny off of the Royals.
This argument is nonsensical. As you rightly note, the money was not personal spending money; it defrayed all costs of government, and if and when more was needed (wartime being the typical example) the monarch had to go cap in hand to Parliament and ask them to levy taxation. So if the royal family want to claim the Crown Estates back that's no problem at all, as long as they understand that the costs of running the state (police, courts, civil service, army, schools, hospitals, roads, security services, etc etc etc) are taken as first dibs and then they get to keep whatever is left over. I mean, obviously what would be left over is a whacking deficit, so sure. They can knock themselves out.
Suggesting that we profit because the royal family worked out that it would be better for them to end the public impression that they were personally responsible for levying taxation over and above Crown Estates funding of the state, and shunt that PR problem off on Parliament completely.... is really contorted logic. You might as well suggest that every PLC is generously allowing the shareholders the company's money when they pay dividends. It was always intended to pay for the state apparatus, and that's what it is used for to this day. On what planet could someone argue that their ancestor's role as national trustee over 200 years ago should entitle them to defraud the descendants of the original beneficiaries of that trust - us?