In formal usage, it should definitely be is: Neither of these options is available. This is the traditional rule (iirc, fowler’s discusses this at length).

I don't want to repeat working in the following sentence: We are working on a working arrangement. These and those can indeed have locative difference. They are the plural forms of this and that, respectively. They often convey a more abstract idea of proximity rather than actual physical …

They often convey a more abstract idea of proximity rather than actual physical …