How many miles on the engine?

cylinder #4 inlet: 8½mm.

That's no problem at all.

cylinder #1 exhaust: 5mm

This probably won't hurt much either until it starts to sound like a Subaru.

Clearly, one of the lobes is well on its way to going flat

Most of the time with stock cams, that damage hapened in the first 20 minutes of the cams life & it's been that way ever since.

Do I run any risk by leaving it as is for a while?

No, just keep an eye on it, especially if it's an old engine.

If it's not that old, then I'd pull it out, clean it all out, possibly need new bearings, probably need an oil pump, hone it, new rings, new or reground K cam & put ity back together again.

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Three 164's, Two 144's, One 142 & a partridge in a pear tree.