317- Welcome to Autopia! Cool car, I always liked those.
That clearcoat failure looks similar to that on my '93 Audi (dark blue pearl). I've beem able to avoid repainting by just 1) doing one good, full detail, 2) keeping it out of the sun as much as possible, 3) being very careful to *NOT* do any more damage/precipitate faster failure, and 4) keeping it very well-detailed in the sense of *NOT* marring the paint any more and always re-LSPing (LSP = Last Step Product, i.e., wax/sealant/coating) it before it needs it (stay ahead of the curve, it really helps).
I would *NOT* aggressively clay it. That's too, uhm...."uncontrolled" a process for my taste on compromised paint especially as it usually involves abrasion. Rather, I'd do a chemical decontamination (I used FinishKare's FK 1119 on the Audi and it worked great, but ValuGard's "A" is more pleasant to use, if weaker), concentrating on the "alkaline" step rather than the "iron-removal"/"acidic step".
While I'm certainly not opposed to the products that are made to remove ferrous contamination, I just don't see it being an issue (or at least not the primary issue) on this older, black car. But the decontamination step I suggested above is something I'd *ABSOLUTELY* do as the first step. Period.
Then I'd do a very careful compounding of the most compromised areas, just to smooth them a bit. Yeah...double-edged sword there as it'll abrade/further thin the already compromised paint. Don't overdue it. Maybe even...don't do it at all! But I did it and I'm glad I did.
Then a Final Polish step to bring up the gloss. Either use a product that doesn't "dry white" in the cracks/etc. or do some sort of process to remove that residue chemically (I wouldn't use FK1119 a second time through, it's pretty nasty stuff). If anybody here knows of a product that does good filling/concealing without drying white, that'd be the stuff to use (I use 1Z WaxPolishSoft but AFAIK that's no longer available).
Then I'd use a LSP that, again...doesn't dry white or else use the wipe-on-wipe-off technique to apply/remove rather than letting it dry before you buff it off.
And of course if you're gonna do any touchup work, try to avoid the "wetsanding to level the touchups" as more abrasion isn't a good idea (I'd use DrColorChips but used like conventional touchup paint rather than according to the directions, or use Langka Blob Eliminator, or just don't bother leveling them). OR just don't bother with the touchups (I didn't on the Audi).
That's what I did to my '93 Audi back in '08 when I got it from the original owner, and it's still looking great (lots of compliments from people who apparently ignore the flaws) in 2016 despite *not* having the obviously-required repaint that I har originally figured it'd need long before now.
That's such a nice car, and Lexus is pretty good about parts (I can't get certai parts for the '93 Audi, not anywhere on earth..

), so I myself would be saving up for a really nice repaint. But IMO you can delay that for a long, long time if you go about it right.