i wasn't aware Saudia (SV) operates Bucharest to Jeddah: I thought that was Wizz territory.

I can't help with information about airside transfers between terminals. But if you are travelling on a Saudia (SV) issued ticket then the timely transfer between flights is a responsibility of the airline. If the connection fails, then SV should make alternative flight arrangements.

I strongly suggest you contact SV (sales office, phone, social media) for clarification of the transfer arrangements. If you are forced landside, there's a visa issue.