Shoghi Effendi was very glad to learn that you devote a considerable amount of your time to the study of the teachings. It is absolutely essential for those who desire to spread the movement to be quite familiar with the writings of Bahá'u'lláh and the Master. Without that knowledge we may be spreading our own views and wrongly attributing to them things that are the result of our imaginings.
Concerning cremation I have not seen anything in the writings. But as Bahá'u'lláh in the book of Aqdas directs the friends to bury their dead, he indirectly discourages cremation. Whether there is some basic reason for such a preference he does not say, but we may try and find it.
`Abdu'l-Bahá does often state that the medical science will much improve. With the appearance of every Revelation a new insight is created in man and this in turn expresses itself in the growth of science. This has happened in past dispensations and we find its earliest fruits in our present day. What we see however is only the beginning. With the spiritual awakening of man this force will develop and marvelous results will become manifest. Among other phases of human learning the medical science will have a place. There is a Tablet of Medicine that Bahá'u'lláh has revealed and which is translated into English. That does not contain much of scientific informations but has some interesting advices for keeping healthy.
Shoghi Effendi was very glad to hear that you are planning to study Persian very seriously. Should you do it you will obtain ample reward for your labours, for you will then be able to go straight to the writings themselves.