Re #1. Wealth quintiles are computed for the de jure household population, not just the population of women 15-49. The proportion of women in each quintile will depend on their concentration in poorer households. The wealth index weight is created by multiplying the household weight by the number of de jure residents. If there are no de jure residents then we multiply the household weight by the number of de facto residents.
In Stata, you can verify the household population quintile weighting is evenly split by checking the Bangladesh household file:

use BDHR61FL.DTA, clear
gen usualhh=hv012
replace usualhh=hv013 if usualhh==0 
gen popwt=hv005*usualhh/1000000
ta hv270 [iw=popwt]
The result produced from this is:
     wealth |
      index |      Freq.     Percent        Cum.
------------+-----------------------------------
    poorest | 15,786.124       20.00       20.00
     poorer | 15,777.318       19.99       40.00
     middle | 15,781.823       20.00       60.00
     richer | 15,783.583       20.00       80.00
    richest |  15,782.26       20.00      100.00
------------+-----------------------------------
      Total |78,911.1086      100.00

(Note: everyone in the household has to be assigned the same wealth, so it is normal that some quintiles will be 20.01 or 19.99 percent).