looked back over your notes to see you're using lnd embeded in zeus. probably can't help with that I'm afraid

The issue with slow payments is probably that your node is making lots of failed attempts. Since unlike in phoenix, you have to route the payments yourself, your node has to try an fail in order to learn good paths. lnd will remember the good and bad paths for next time though so hopefully that helps.

I think mutiny does it better since they provide a pruned view of the network for their users with their gossip sync. lnd does have a hacky version of a gossip sync that blixt and zeus use (it's called the speedloader irc) but it would probably not be trivial to do what mutiny does and add probing information to that.