This is a challenging and mix case.
I think u are quite a competent parent, so let me get u some idea in deeper explanation personally.
Let me start with non-development delay part ( i personally think it is more important this time), it is a problem of signalling which affect sub-consciousness psychologically. Let me get u an example of a true story to be easier to understand. A kid about 10 yrs old is wetting her bed while sleeping at 11am exactly every night. The reason is that every night at 11am, she sub-conciously heard her father closed the door and went out to meet his mistress (before she heard the fight btw parents perhaps) One day, this little girl mistakenly pour water in her bed.To clean up her bed, her father did not go out that night. After that, she unconsciously wet her bed every night since then and kept her father stay at home successfully. Of ocurse, it turns to be a behavioural problem of this girl.
Go back to yr case, u should ease yr signal GRADUALLY when he is doing his homework. Firstlly, beating is the worst signal. MUST stop immediately. U are lucky that yr kid did not have much behavioural problem over beating. Many just learn beating from parent to other kids. However, is yr kid thinking that he dont need to do homework properly if no one beats him???
Other suggestion u might consider,
when guiding him to do homwork, only do correction after he finished each one. Let him bear the time & results he needs to make correction.
If keep going ok & his attention is not so bad, u should leave 1-2 mins at his sight when he is doing homework every time and come back to check on him in the beginning.
Other more advanced suggestion talk next time since it is too long.
On the other hand, yr problem about yr kid want to learn everything but not properly. I believe it is a problem of EXPECTATION & THEORY OF CHOICE, talk next time if u want to hear.
As said by ababymami, positive reinforcement, like a chop, a sticker or even writing a little star will make a gd sign for work.
Two more parts u need to consider:
I myself also did my work fairly without the sight of my boss. It is human nature (It is leisure against return in economics. Should I say fortunately or unfortunately??? My son is totally different from me. He tends to disregard environment, focusing on task & goals only)
Also, pls remember. If u ask a kid before 6 why u cannot steal, or cannot skip school. Their answer is police will catch him or teacher will punish him. Not becoz it is a misconduct. Signal is overwhelming his judgement on decision before 8 in many cases. If u want to improve his self -discipline, the first step is to let go of him and reduce the influence of outside signals. Handing him an eraser for self-correction is a gd beginning. More advanced is that u could deny his incorrect answer and revise with him together before or after received the comments of the homework. U could sometimes even read him some story book with missing or wrong pronounication inside (It is ok whether u told him in advance) for him to gain self-recognition & self-guiding sense.
2nd- no one will hear reasoning pls remember. I could tell u even an adult like me wont listen to a reason or consequence of a behaviour esp it is happened in FUTURE. Kids is even worse since they might even not understand what is a reason and more importantly, their sub-conscious is largely over-whelm conscious before 20something. That's why there are very common behavioural problem for kids and juvenile in society. All those bout 我已經同佢講過千次萬千, 上左小學咁樣做, 你每日都要留堂, 遇著考試, 你求其笞完就算, 做錯晒, 係要補考, 浪費自己時間, 佢呢頭話唔會再咁, 果頭又係咁,
No kid will listen even u told him every minute coz ALL kids wont take any care of a teeny tiny expectation on what they are NOT interested.
Simple solution is a clear instruction and clear IMMEDIATE NATURAL consequence like proper homework ~ a time of play or reinforcement.
But be as calm as possible if not successful. (Hahaha, though I told u to be calm, I myself lost temper alot. So I could only say as much as possible la)