Your questions are very specific, and I doubt anyone here will know all of them.
Just a few marks from my side, then:
With a broken feet and such connection, they probably expect him to stay in the E gates area.
TLV arrives dirty, ie you'll need to pass security upon arrival to head to the E lounge.
Personally I don't think they'll be happy to transfer him landside (probably could be arranged, though) since it would involve much more time and distance than "just" bringing him from airplane to lounge and back. As compared to all the way to arrivals, and then picked up again from the checkin area. Would definitely needs LOTS of preparation to have everything arranged ahead. Seeing your flight is tomorrow, I'd rule that out to actually work.
The lounge itself is perfectly wheelchair accessible, all can be done by lifts between gates / security / lounge etc.
I'm not sure if you could "rent" a wheelchair from the airport - my understanding is that's not a default option, but you can always inquire. But be ready for a "no".
You can stay all day in the lounge. Just not overnight
No one will care. The business lounge in E gates, while being fine, is probably a bit boring for 9 hours though. Especially since it's lacking the whisky bar next door in the *G lounge
IF you decide to go downtown, there is quite some walking involved to catch the train. It's all possible by lifts, and you'll arrive in the city centre within a few minutes by train, but most sight seeing isn't THAT easy without walking much. Doable, yes, but I'm not sure how easy it will be with a broken feet. But "basic" sight seeing definitely will be possible.
I'd suggest the following: Take the Tram downtown (line 10) - some sight seeing on the way already this way. And it's easy to catch it in ZRH.
At ZRH mainstation, get into a tram that goes to "Römerhof" station, then take the funicular up the hill for a stunning view of Zürich. Alternatively, you can take the S-Bahn service to Üetliberg. You won't get to the very top, but already enjoy a nice view riding it up. Since you'll be arriving early, no ship that early, but during the later morning, there will be several "round trip" boats doing trips on lake Zürich. Absolutely a must even without a broken leg, even more so with a broken leg since it involved zero walking while on the boat
Weather tomorrow will be fine, I'll myself be in the area. If you fancy a local "guide", let me know (PM)
About your seats, I'd say they're fine, and unless they swap for a A32x, I'd leave them as they're. You can always inquire about bulkhead seats, but 5AB are good (Stübli) and on the TLV-ZRH routes, expect many elite members already having snagged the good seats.
In any case, arrive early in TLV (3hrs being the absolute minimum) - checkin is closing 2hrs before departure. Having wheelchair assistence will make the queue at the security counter much faster, though.