The DHS surveys use "Normalized" weight which is a relative weight without scale, the weighted number of cases (household, women and men) will be exactly the same as the unweighted number of cases at national level, as you found. This means that the weight variable in the DHS data set will not be valid for estimating population totals, it is valid only for estimation relative indicators such as means, proportions, ratios and rates. In order to estimate population totals, the weight variable must be rescaled. I believe the weight rescale is a popular topic in the DHS forum, you can search for the word "weights" to see other messages regarding this topic.
I am not clear with what you mean "with objective to get the population currently attending with reference to Rwanda Population and Housing Census 2012". If you can specify your problem more precisely, let me see if I can be further helpful.

Thanks
Ruilin