Outside of casual region-locked content access, don't rely on VPNs for that sort of thing. Most sites, even the dodgy dating sites, usually flag you for using a VPN IP range.
For more popular sites and services like FB dating, VPS won't help you at all. Besides, they pull location from your device's GPS and not just the IP. Go use GPS spoofing apps for that. Just make sure the IP, data, timezone, is consistent to what you set the location to.
Also, make sure Facebook has location permissions enabled or it might fall back to old location data. Also also, clear app cache or reinstall after changing location to force an update. It’s a bit of a process, but it works for most people doing regional testing or projects like yours.