Good writeup!
There are two questions where I would want to know a little bit more:
Will casual users be able to accept payments and donations without having to run their own full node 24/7?
Currently, it is not possible. It might be possible in the future to ask a third party to watch for the incoming payment.
Here I would like a clarification what is exactly not possible. Can't the payer
initiate a Lightning transaction, waiting a time (e.g. 24 hours) until the other node pops up to sign its part? It's clear that both have to be online at the same time somewhen, at least for a moment. And: Does the "watching" node need to be connected with the destination node?
Is there any risk in running a Lightning Network node?
Yes, due to many factors. Lightning Network implementations are still in beta and might contain critical bugs which could be used to steal funds locked up in channels. Keep in mind that if you won't keep your node online 24/7, someone can attempt to cheat you by broadcasting an old state of your channel. An online node would normally broadcast a penalty transaction.
Here an interesting addition is if there is a "standard" timeout/lock time for the Lightning "penalty transaction" - to know how often you should be online to avoid being cheated. I've currently no Lightning node running (I tested Eclair some weeks ago but it's now outdated, so I can't answer that question myself.) Normally, you should be able to set the timeout you want, but what are the chances you will find a route or a partner to open a channel with?