Rambam Kiddushei Kesef is divrei sofrim?

 Rambam (1:144 Pe’er Hador) Why is marriage through money described in Mishne Torah (Ishus 1:2) as divrei sofrim (rabbinic) while intercourse and document are described as being from the Torah because  in fact all three are learned from the Torah? The answer in brief is that I have a sefer in Arabic concerning the number of mitzvos, It consists of 14 chapter dealing with major principles dealing with the counting of the mitzvos.  It is needed to be understood first in order to be aware that your question is mistakened as is the counting of mitzvos by everyone besides me up until the present time. I explain there that not everything that is learned from a hekesh or kal v’chomer or gezera shaveh or one of the 13 hermeneutic rules has the status of a Torah mitzva unless our Sages indicate that it has Torah status and this is also true of what is called Halacha L’Moshe M’Sinai. . In other words a mitzva has the status of Torah only if it is explicitly in the Torah or our Sages indicate that it is from the Torah. Intercourse is obviously from the Torah while both money and document are learned from drash so why do I only state that money is divrei sofrim? We see in the discussion in the gemara (Kiddushin 9b) that marriage through document is treated as a Torah obligation since an engaged maiden who was married through document is liable to the death penalty if she was unfaithful. 

Rashi (Kesubos 3a) I heard all my teachers explain that marriage through money is only a Rabbinic decree. But it is impossible to say such a thing, because it is in fact learned from a gezera shaveh from a Torah verse (Kidushin 2) which is equivalent to learning from an explicit verse. Furthermore if marriage is only Rabbinic, ‘how could it result in the punishment of stoning and cause an unsanctified sacrifice being offered in the Temple if adultery is not intentional. 

 Rashi Gittin (33a) I received the ruling from my teachers that marriage with money is only rabbinc since is not stated explicitly in the Torah but is learned from kicha kicha of the field of Ephron

Tashbatz (1:1) Many people think  that the Rambam's statement that marriage through money is Rabbinic because he accepted the view of Rashi’s teachers as Rashi notes in Gittin (33a) but that is not so. We know that the Rambam himself wrote a tshuva that explains it and further more Rashi already refuted that view. Noting that something learned from a gezera shaveh has a Torah status.  

 Lechem Mishneh (Ishus 1:2) And with money which is Divrei Sofrim. The reason the Rambam said this is because whatever law learned by the 13 hermeneutic rules is called Divrei Sofrim as he wrote in his Sefer Hamitzvos. However this answer is problematic since document is not explicit in the Torah so why isn’t it also described as Divrei Sofrim? The Rambam addressed this question in a tshuva cited by the Ramban regarding counting the mitzvos.  He answers that document is clearly a Torah law as is seen in Kiddushin (9a)

Kesef Mishneh (Ishus 1:2) A woman is married in three ways by intercourse or document which are Torah methods while the third – money is rabbinic. This ruling of the Rambam is problematic, How could he write that money is only Rabbinic since it is learned from the Torah by gezera shaveh? It is known that what ever is learned by one of the hermeneutic rules is a Torah law.  I found that the Remak testified that the Rambam himself corrected this text to read that all three were from the Torah. I found a similar claim by the Rambam’s son. Nevertheless it seems to me that is not correct based on the fact that the Rambam wrote in the third chapter of Mishneh Torah and what he wrote in his Sefer Hamitzvos.  The reason that the Rambam wrote that it was divrei sofrim is explained in his Sefer HaMitzvos in shoresh 2 that laws not stated explicitly in the Torah are called Divrei Sofrim this concept also is stated in Sanhedrin (88) that something not stated explicitly in the Torah is called Divrei Sofrim – even though it is considered a Torah law. Rashi (Kesubos 3) states a similar idea.