Does FAA recommends specific maneuvers for complex endorsements?
To answer question #1:
A complex endorsement is just that. It’s an endorsement. There are not any prescribed maneuvers to receive the endorsement. But, the instructor is holding himself liable for your performance after receiving the endorsement. Primarily, the areas where that liability may prove hazardous to the instructor, their certificate and career is on every single one of your takeoffs, landings, and go-arounds after the instructor is no longer in the aircraft. The flows and checklists for that aircraft have to be consistent and second-nature to you even without the instructor’s prompting.  

A 2 hobbs-hour flight from start-up to shut-down is typically the limit of learning for most people. Two 2-hour flights along with a couple of hours of ground instruction seems reasonable for satisfying your instructors confidence in your ability. That is all conditional to your actual performance. It is also a very subjective assessment. 

To answer question #2:
As far as correcting someone with more knowledge and experience than yourself, that can and should be done if (big if) they are wrong. Many things in life and aviation are subjective. There can be multiple right answers. In the case that an instructor gives you a wrong answer, be courteous and cordial in your correction. But, your answer must be backed up with fact. You should question your own answer until it can be: backed up with a regulation or recommendations out of the FAR/AIM; documented from an FAA handbook, publication, advisory circular, or other official document; referenced from the POH, AFM, owner manual, or other manufacturer source; cited from a reputable source.  

If the question can not be answered objectively, the answer may only be a matter of opinion, style, or personal technique. Or, it could be a quirk of that particular aircraft or environment. Either way, it would probably be best to tailor your training to the criteria of your evaluator. 

Remember, your instructor is human. They are fallible. But, so are you. And, they have been doing this aviation thing safely way longer than you. But, regulations do change. Take a slice of humble pie before you have to eat crow. You both may learn something new or improve upon something old. And remember, a good pilot is always learning.