My brother thinks I have disabilities that make me unable to do my job and is upset I got an advanced diploma, even though i can barely read or write, AITA?

I 25F, (I think, I get confused about what numbers are, what the represent, the difference between bigger and smaller numbers) have an older brother, 58m, (is he really older though? numbers, big small, what do they mean? Is 58 bigger or smaller than 25?) he is prone to ostentatious pomposity and use of grandiose superlatives when describing his advanced intellect and acumen, and can be supercillious, so sometimes i think he is a bit of a cockalorum.

I have begun to percieve some concern on his part that I may have been employed above my aptiditue and that my skills may be incommensurate with the exigencies of my role. He asked me about this and it was not a question I adequately learned a response through echolalia, generally i don't understand almost any words, spoken or written at all, but have realised that some responses cause positive responses in others in certain circumstances and use those responses depending on the context I pick up. Due to my inability to answer I became enraged and confused and began to vociferate incoherently at him.

Subsequently I began to cogitate on his words and concerns and consider the possibility he could be correct. After all, I had understood nothing of the questions asked in the interview for my employment, I was repeating parts of the questions and words I had heard before with no idea what was happening, or even what my role entails. It began to concern me as I have a great deal of responsibility as I work with children with SEN, some have complex emotional disorders and I am completely and irreveocably defficient and ill equipped to manage their needs, as i dont even understand what is happening from moment to moment. Like these words I am typing, complete nonsense to me, or those words, they are also beyond my ken, or those words, but i could get stuck in repitition ad infinitum if i keep listing the things I say that I dont understand.

I have been like this for some time, when I was 3 i would perambulate aimlessly around the locale, the envrions of my home were unsafe for such activity, with trains and roads in the vicinity.

So, AITA? Should i give up my profession and perhaps stop pretending i am able to walk and talk and feed myself?