In a 13-seat constituency 1/14 of the vote, or just over 7%, guarantees you a seat, though you can get away with less than that. Or, rather, 1/4 of the vote after discarding the votes of even smaller parties.

In 2004 the Swedish People's Party obtained one seat with 5.7%, which is less than the 1/15 you need to guarantee a seat among 14, even after discounting the 6.5% of the vote obtained by "other" parties.

The SPP indeed got the last MEP. The next to last was the Centre Party's 4th MEP with a d'Hondt quotient of 96543.5 votes, over the SPP's 94326. The SPP only needed to increase its vote share to 5.83% to get the 13th seat. This is only 2.2% larger than the 5.7% that it did get.

Belgium does have minority constituencies. The German-speaking minority is tiny and yet it gets to elect one seat in the EP. So there is clearly a precedent.

We have met the enemy, and he is us — Pogo