Take a look at this: http://www.forgottencats.com/

I found them on a Google search. We took three barn cats
to them. There are similar organizations in various places.

150km is ridiculous.

And not all vets are as particular as yours.

On the other hand, if he's a tom, you may want to just
leave him fertile. He'll never have kittens, and in a
world with un-spayed females if it isn't him that knocks
'em up it'll be another.

I'd only neuter him if I intended for him to come indoors,
at this point, especially if it required driving that far.