Regarding serving your godbrothers, this is a very good practice. The Spiritual Master is never without His followers, so to serve the Spiritual Master also means to be the servant of His disciples. When you want to serve the king, you must also serve his minister, secretary, and everyone who serves him. And to serve his servants may please him more than to serve the king personally. So the Spiritual Master is not alone. He is always with His entourage. We are not impersonalists. We take care of every part of the whole, as much as one should take care of his hat as well as his shoes. Both are equally important for the upkeep of the body. I hope that you will understand this rightly.
It is important that we preach the message of Krishna Consciousness exactly as we have heard it from our Spiritual Master. The same philosophy and spirit must be there exactly. Just like we preach in this country exactly as we have heard from our Spiritual Master, but there are changes due to the time, circumstances, and the trainees. The spirit of the disciplic succession may not be changed, but there may be adjustments made to suit the special circumstances.
Regarding your last question about the importance of chanting; this chanting process is the only way of attaining full Krishna Consciousness in this age of kali yuga. Lord Caitanya stressed upon this point, and we may take it from His authority that no other method will prove to be successful in this matter.