How to contact the 'AKADEMIO DE Esperanto' and suggest them to simplify/overhaul/revolutionise the Esperanto language by making plural forms, object agreement and other confusing language parts of the language optional? Can somebody rule a petition to convince the 'ADE' to make change to the language?
I'm a member of the AdE, but I'm writing here as a private person.
First, in order to answer the question in the title, here is the contact page of the Academy.
Second, in order to react to your proposed reforms, here is my advice. From the content of your question I assume that you don't or hardly speak Esperanto. I urge you to learn the language first, for several reasons:
It is good practice in the Esperanto community to discuss reforms in Esperanto only, as this a) keeps trolls away, b) shows that the proponent has an understanding of what they want to change, c) keeps quarrels away from the outside world. Discussing reforms in English will get you bunch of responses much less polite than mine.
You will be able to read the Preface to the Fundamento de Esperanto, a document that fixes the core norms of the language (like all phenomena you mentioned in you question). You will get to know the way how Esperanto can evolve and you will understand that the Academy can add new rules to the Fundamento, but not as a replacement of older rules and only in case of indisputable need. The mere wish of a few beginners is not a sufficient reason to do so. See also the responses to this question.
You will learn that Esperanto is a fully-fledged language with a community of speakers who are very reluctant to accept major changes, just because Esperanto is working well already. You will see that the chances of the reforms you propose are nil, so you will either live with the language as it is or leave it altogether instead of wasting energy fighting for a lost cause.
You will have the chance to see from practice that some of the alleged flaws of Esperanto in fact are strengths.
You will have access to a decent amount of cultural products like literature, music, and meetings not available in English, which make it worth learning the language independent of its role in international communication or structural details. It's fun, believe me.
A quick search on Google will find their website where you can contact them.
However I believe in general the Akademio doesn’t make sweeping changes like this. Rather they follow changes to the language as it used and make minor official recommendations when the usage diverges. Therefore if you want to make changes to the language your best bet is just to start using them yourself and try to convince others to do the same. If enough people do it then eventually the Akademio will officially recognise it.
On the other hand if you propose extreme changes such as this then the resulting language probably isn’t Esperanto anymore and you are making a completely new constructed language. This has of course been done many times already and only time will tell if any of them will gain more support than Esperanto. Take a look at Ido, Toki Pona and Pandunia for example.