Great thread and discussion. Lots of good stuff in here. You've received some excellent feedback and suggestions.
Two important points though:
1) Running by feel is on the art side of this, as opposed to the science side. But it has its underlying basis in the science. It can be a challenging and difficult thing to learn, but well worth the effort. Your body will thank you, and will perform at a higher level for a much longer time.
What does that mean in the practical short term? Back off the pace on the tempos, make sure the easy runs actually feel easy, and don't be afraid to leave the watch at home for a week or two.
2) There is an elephant in the room that has only gotten one very brief mention so far. (I'd like to say that surprises me, but it doesn't. After all, this is LR.) Or maybe I should say two elephants.
You said you did an easy 30 mile week immediately after outdoor season ended, and then started your buildup to 50 miles. Does that mean you took no break at all after outdoor season?
And all your schedule variations show you running seven days a week. Meanwhile your body is clearly telling you it's struggling right now.
I'm not trying to be a wise a$$, but listen to your body. It needs more rest/recovery than you have given it.
At the very least, start taking one day per week completely off. This is really important, and will pay big dividends.
If you took no break at all after outdoors, you should consider a mini-break right now of two to three days, followed by shifting into a six days a week running schedule.
Call it running by feel. Call it listening to your body. You can call it whatever you want. But the most important thing to call it is smart.
Good luck!