Indeed I am burdened. I just finished reading the Lotus Sutra and nowhere in the Sutra is any mantra given. So your practice of chanting Myoho renge kyo was not given by the Buddha.
The Lotus Sutra does convey the Great Law of Buddhas, the law of the first vehicle, but it is not a mantra. It is all found in Chapter 2. By the way, as you should know, the Buddha in that chapter says that he has already fulfilled his vow to make us all Buddhas. To quote, "I have converted all living beings and caused them to enter the Buddha way"
If that is so , then what's the point of preaching a particular way. We are all already there according to Buddha. However, seemingly in contradiction in Chapter 28 he indicates 4 conditions necessary for anyone to acquire the lotus sutra.
Most interesting to me was the law of expediency. This is apparently the law of 3 vehicles where we are taught to make offerings to the image, any image, of the Buddha. The offering can be most anything- drumming, flowers, food, etc. This law is meant for us who cannot comprehend the highest great law. All previous Buddhas had taught this way. When (in Chapter 2) our Buddha decided to also teach by "the power of expedient means", then all the Buddhas from the 10 directions appeared before him and said that now he had "attained the unsurpassed law".
Well, none of this sounds anything like what you have been telling us. Can you resolve these discrepancies. You already resolvedone. You chant is in Japanese or maybe Chinese, not Sanskrit. That already is imperfect.
The bottomline as far as I can tell is that you become a Buddha if you use any expedient means to teach about Buddha, or God in my opinion. So all mantras, and even using the internet, is acceptable. But let's not be black and white about it. Even the Buddha attained the unsurpassed law when he used approximate means to teach. Let's realize, in consonance with the Buddha, that any human technique is expedient or approximate, and that all means are acceptable. Some are stronger than others, but all aim in the same direction.