Here is another idea, lets see if it can be done or has any merits to it.

If we know the exact start and end range of a public key, we could divide the end range by a number to reduce it down as much as possible, maybe making it a 6 digits number, now we only have to change our 6 digit number and multiply it by the number which we first divided our end range with, we need to change the numbers in a way that it never goes beyond our end range when multiplied.

Now, before doing that, we need to add and subtract 1 G to our target and divide the results by 2, e.g. if our target is 256, we add 1, 2, 3, 4 etc and divide them all by 2 also we will add n/2 to all the results just to be safe and keep all of the keys to compare with our multiplication result.  Eventually if we change our nonce, ( 6 digit number ) enough times and multiply it with powers of 2, 3 etc somewhere we should see a known key.

A simple example :

Start range 1, end range 512, our target is 95, now we divide 512 by 32 to get 16.

But first lets generate some offsets for our target.

Add 1 to 95 = 96/2 = 48
Add 3 to 95 = 98/2 = 49
Add 5 to 95 = 100/2 = 50
Sub 1 from 95 = 94/2 = 47
Sub 15 from 95 = 80/2 = 40

Now we have 48, 49, 50, 47 and 40, then we multiply 16 by 2, 3, 4, 5, 6, 7, etc until we see one of the keys above.

Imagine if we generate different offsets, like billions of them, then we could simply keep multiplying to find one of our targets.

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This just came to my mind today, it's not cooked well , yet!😉