Okay, after a lot of research...I have come to a sort of conclusion.
For one, I believe it would be more accurate to call the Axumite Kingdom either "Daamat" or the "Kingdom of Daamat" Either way, it was a kingdom. The reason for this is, most scholars agree that the Axumite Kingdom started around 1 A.D., though there is some debate and others say the date is between 300-50 B.C. As for the D'MT Kingdom (Daamat is one way that people think it was pronounced), it is thought to have began around 800 B.C. and ended around 300 B.C., so which one to chose is still questionable. Personally, I believe Daamat should be used, as Axumite Kings are known only from 100 A.D. onward, and that will solve my problem on finding the ruler's name. If you do this, which I highly recommend, you should change the civilization to one that is "religious" and "industrious." Religious, I am sure of, as they have extensive Stelae/Obelisks, but "industrious" I chose because there is no information pointing to them being commercial, scientific, or military, and industrious is most likely true as they were able to construct large obelisks. Second of all, there needs to be the addition of 2 more cities (Kaskase and Addi Seglamen), which will require some re-arranging. The capital should still be Axum, as it existed before the Axumite Kingdom, but the name and characteristics of the kingdom should change. Also, I have found out a possibility of four rulers (we'll need to add vowels, but that shouldn't be too hard). The first is Malik W`RN HYWT. His three successors that we know of used the title of Mukarrib, and were (in order) RD'M, RBH, and LMN. Whichever one you pick is your decision, but I think I should fill in the vowels, as I have a better feel for Ethiopian names, though I'm unfamiliar with these ancient names.
The new city layout should be like this unless you have any objections (actually, the first layout I gave you was off a bit because the map seemed a bit inaccurate to me, and I had trouble locating areas. Again, this is still a bit inaccurate in order to fit all the cities in):
Marib - No change
Aden - No change
Axum - No change
Yeha - No Change
Adulis - No change
Metera - No change
Kohaito - New coordinates - 79, 161
Kaskase - New coordinates - 77, 163
Terrain/Irrigation and Road Changes:
Terrain (major change) - in order to make the scenario more accurate, you'll have to change some of the deserts near Daamat to Flood plains. The reason for this is, the desert that is there today used to be a fertile area with a lake 150 feet deep, but it dried up over the years and became a dry, barren salt bed. During Daamat's existence though, it was probably a lake, and would be better represented as flood plains. The coordinates I suggest should be flood plains are as follows, but you can chose not to use them if you think that's best:
(79,165), (80,164), (79,163), (80,162), (80,160).
Others you will just have to look at the map because I really don't feel like saying the added roads and irrigation.
This means a city order change from what I posted earlier... you should now add Kaskase and then Addi Seglamen (in that order) right before metera
Edit... Keep Addi Seglamen in the cities list, but I decided not to
use it as a city
Also, Daamat shouldn't have tactics even though the Axumite Kingdom would have had it.
Finally, cultures and improvements shouldn't change for anybody except for a few exceptions:
Marib - Culture = 100 (forgot to do this earlier, but it is correct)
Metera - City Improvements - Aqueduct (again, forgot to do it)
Kaskase - City Improvements - Granary and Temple, culture = 10
Yoda, I uploaded the file to Civfanatics under the name "Classical World2D.bix"