Thank you for the effort you put on this. But I have 2 concerns on the work you are doing.
a) In current Unicode page the letters which are not in contemporary
use have been dropped. So I believe as the numbers in question are
also not in use, the same rule should apply to them.
b) The signs you have taken from the sources are not real numerals. In
ancient literature, combinations of letters have been use to represent
numbers. When they group in a particular manner they have interpreted
as numbers. Those letters have been evolved and changed to the current
shapes, but the practice of using letters for number has been dropped
with the increased use of Arabic numerals. So the signs which you
referred to as numbers are old Sinhalese letters. There should be
corresponding letters for the same in the current alphabet. A good
Sinhalese scholar will be able to help you to identify what are those
letters. Basically by putting them on the code page, we duplicate the
same letter twice, the contemporary one and the older one, which has no
meaning. (this info is based on the details I gathered from several Sinhalese scholars)
I will try to get some more information on this and let you know.
Also I copied the mail to Sinhala-Unicode@googlegroups.com
related conversations going on in Sinhalese. That group also will be
helpful in this regard.