every dobin/dosbin/doexe/doins in src_install should be followed by an appropriate "|| die" a lot of the commands can be combined (all of the dobin's can be combined into one as can all of the dosbin's)
Yes, better error checking would be nice to have. I'll work on that the next release. But have you seen any errors with the existing releases? This is the way the ebuild has _always_ been.
assuming that it has always worked and never failed is irrelevant
Will be fixed in 090 release.