I have never heard of exportworthy. My 3,200 page unabridged Webster's has no record of it. A regex search for "^export[^ ]*$" at dict.org shows:
web1913: Export Exportability Exportable Exportation
Exported Exporter Exporting
wn: export exportable exportation exporter exporting
Search engine hits are not proof: there are 50 times as many Google hits for "droolworthy" as for "exportworthy", and "droolworthy" is not a word, either. Driveworthy, drinkworthy, sunworthy, moonworthy, eatworthy, drinkworthy, shineworthy, deskworthy, momworthy, dadworthy and burgerworthy all have some hits, too. None of them are words.
But this gets into the whole question of "what is an English word?" which has been addressed numerous times. If ten million Germans use the word "Handy" when speaking English to mean "cellphone", is it an English word, or not?
Seaworthy is always written as one word.