Pls, check my feedbacks. Lot of openwrt-projects, implementing hotspots. Always used coova-chilli for these.
Although your budget is far too low for me, I might be willing to do this, because of your country.
Can you provide ssh (root) to your openwrt device (a router, I guess, not just a modem) AND into your server running RadiusDESK ?
Which openwrt-device are you using ? Detailed info, pls, incl. version, if applicable.
Pls, provide these infos via chat, only.