There’s no real way to fix the first issue. As you’ve said, it’s been a known problem for more than a year and Apple hasn’t deemed it important enough to resolve. The only solution I’ve seen suggested is disabling iCloud syncing for Safari, which is kind of the whole point of the thing. It also costs you your synced bookmarks and history, of course. You can also quickly CMD+L, CMD+C to capture the URL before the tab is gone again.
I was able to get tab syncing working by disabling and enabling Safari in iCloud settings on the offending device.
Apple really doesn’t seem to care about making Safari reliable so I switched to using a browser developed by a company that actually has a stake in making sure their software works.