I agree with you that vocabulary is not easy to memorize. But I think your target of 10000 words is a bit ambitious. The higher level of HSK (level 6) contains only 2500 words. This is probably a common basis of vocabulary and you certainly need more but on specific areas depending on your work or interests ( medecine, sciences, music, politics, economy …).
Regarding grammar I am sorry to say that I disagree with you.
Grammar is not that easy.The fact is that there are a lot of things in an english grammar which simply does not exist in chinese (conjugation for instance) but there are very strict syntax in chinese, words order (都不 versus 不都), measure words (量词), so-call empty words which do not translate in english (such as 了，就，的，地，得 and so on), use of auxiliary verbs (要，会，能), resultative verbs ( 了，到). The complete list is too large to be given here. I have a chinese grammar book (in french) which have more than 500 pages.
Maybe I misunderstood what you mean when you say “grammar, which I don’t need” is it because you thought it is useless or because you already know.
In any case, grammar is not an option, if you want to be understood you need to be grammatically correct. If your pronounciation is not perfect, with a good grammar you still have a chance to be understood otherwise no way.