Since I have no patience, I’ll lay out some items for consideration.

1st, I wouldn’t rely on an ISP router to serve as my end point for a VPN. They likely have access to manage that device and it likely isn’t getting any updates. You are better off implementing it with your own equipment that you keep updated.

If you have a capable security device serving as your router to the external internet and you want full access to your internal network, then you might consider using a VPN that terminates at your router.

I myself am a fan of setting up a jump host and initiating a VPN connection directly to that host when using an agent based solution. Then you can monitor the host for activities, more easily keep your edge device patched, and then use the capabilities of your jump host to interact with the rest of your network. This would require either an agent to periodically poll a platform for connection requests or another form of ingress into your network.

Expand on your use case. Why/what do want to access on your local network when you are not there?

Omg, I agree. I hate seeing the same article posted to 10 different instances all lined up in a row.

More than 5 posts would raise the likelihood of people blocking that instance because of spam. Less is more.

It sounds like you are looking for a server that is ripe for bot abuse. What time frame did the admin say not more than 5 posts. I would tend to think they mean 5 posts a day which sounds completely reasonable to be for an upper limit on posts per day into a single sub.