Kangaroo can find a key in any range, regardless of its size. Even if you specify the wrong range, kangaroo will still find the key, but it will take much longer.
JLP's kangaroo implementation does have a problem with small ranges because by default there are too many kangaroos in a small range. You can adjust CPU/GPU group size to fix it, search with cpu only, or search with less threads/grid size.
Regarding searching for multiple keys, the kangaroo algorithm only works with one key at a time, so such a search is only possible sequentially. If it were possible to search for several keys simultaneously without loss of speed, then the puzzle's addresses with revealed public keys would have been solved long ago.
so the problem still lies in choice
we have none to make but to keep trying
we are all victims of causality
let's give the solver of 120 and 125 some more time, they'll solve all the puzzles with the exposed public key before anyone is able to solve puzzle 66
even the solo pool is only 3% gone from the search range despite the fact that we scan in bit ranges randomly
the truth is the only way to go is the puzzles with the private key and so much investment to go all in
and if anyone could stack up 100,000 4090s in a single machine which I don't think is possible. then the search would take approximately 20.5 hrs using KeyHunt Cuda (36893488147419103232/100000/5000000000/86400) but if you do the maths towards how much renting 100,000 4090s would turn out to be $830,000 (20.5*0.4*100000) using a standard rate of $0.4/hr for a single 4090. let's just imagine that the key would definitely not be at the last part so we can say 50/50 chance of getting it sooner before the last part which still leaves us with an investment of $415,000
now the target is how much again?
How much profit would you be making?
It's practically impossible to invest any amount of capital in the search for puzzles without the exposed pubkeys while still expecting to make any profit
and mind you "even if you have the private key for the rmd tahts have exactly 39 characters as that of the puzzle 66" for example "20d45a6a762535700ce9e0b216e31994335db8a4" and you thinking searching that range would get you closer to the range of puzzle 66 then you definitely don't understand how sha256 and ripemd160 works