The phrase ‘Subjective Realism is True’ contradicts itself. By saying that it is true, you are admitting to an objective truth. That is why, once you internalize the idea of subjective realism, and you think it is true, you therefore must realize that it is false, for you have just admitted to an objective statement.
We cannot prove that we exist except by the very fact that we are self aware. Cogito, ergo sum, “I think, therefore I am” sums this up perfectly, because by virtue of thought we can know without a doubt that we exist. We need no proof because the thought itself is proof. Even if we have no proof that our bodies or souls exist, something does exist because we can know that we, at least our core being, exists. And as for someone else feeding us thoughts, if we are truly thinking beings, (not necessarily physical ones, but thoughtful ones) then we are the originators of thoughts by definition (again, let us not label the word thought, and rather the idea. Whether or not our expression in words is accurate, the idea of the definition of the word is what we must concentrate on here). We would not be able to think about ourselves if we were fed these thoughts, even if the thoughts we were fed told us to do it, simply because thought, by its very being, requires the originator to willingly create these things that we call thoughts. Assuming that robots exist (which I know is up for debate - but for the sake of a metaphor), we can program a robot to ask questions on why it exists, but the robot will never ask one of those questions on its own accord, and never actually would think about the questions he’s asking. He would never even be under the illusion that he thinks so, because by being fooled, he would have to have independent thought. This is, of course, assuming that humans cannot give the power of independent thought to someone and is asserting that we cannot give the power of independent thought along with orders that cannot be disobeyed.
That is not to say that we did not get our thought from somewhere else, but once it was given to us, we had to have taken it as our own, and the point we are at now, by mere virtue that we are arguing this, is after that fact.
And I do say that if you believe reason does not exist, then you have rendered any argument of yours null, because by saying that reason does not exist, you undermine your well-reasoned argument. My argument, simply because I argue that reason does exist, lends itself credibility.
As for your self- admitted ignorance, humility is a very appealing and good trait for any true philosopher to have, but I would say that the goal of a philosopher is not to question if everything exists, but to search for all knowledge. In order to do this, though, you must first prove existence at all, which the Greeks did using their term “Cogito, ergo sum.”