Thanks for this post. Apologies I have not had to read through in detail, but I would suggest that perhaps:
The search criteria that you have used has missed a significant number of papers within the field. Looking at the country distribution you posted, this becomes more obvious; I would suggest looking at the What Works papers that were produced several years ago, where quite extensive literature reviews were being conducted
I think you do acknowledge this weakly, but there is such wide-spanning heterogeneity in the studies that you have included (and the programs the use), that I think tighter sub-group analysis is needed to tease out meaningful conclusions
A lot of work in this space has been done in the last 5-6 years; whilst not a specific limitiation of your work, just something to bear in mind!
DM’d you