I will put it here. As stated, and just to confirm, I downloaded an installer from your store. 250 Kb, running installer gives me same down load speed, lucky to top 275 kb. Down loaded from another store 3Mb. Tired 4g phone tethered to bypass all my network, same thing. So it is not my provider because 4g bypasses all of that and other store I believe in US worked fine. Now if it is true that you have servers in different countries, is it possible in your installer to allow us to select which country to down load from, it may solve this issue since I have no idea where your servers are. And if we have a known bad one than we can pick another.
Australia in Sydney NSW dont know how other sates are doing not sure if VPN will fix. DOnt use VPNs
Thanks