I don't know about the First service, I've not done that (Brunch + Bistro maybe).

I was surprised there's nothing in the Dashboard about the Jeddah lounge. It's basically a shared lounge that many / most airlines other than Saudia use in Jeddah, which is a crummy airport compared to RUH, though surprisingly small. The lounge is called the First Class Lounge, but everyone uses it for all premium tickets/status, and it's sub Galleries Club in terms of quality. Snacks and soft drinks, though you could get yourself some Saudi Champagne if you wish (Perrier, mint, apple and / or orange juice) though there may be some in in clear glass jugs in the fridge. Due to the emigration checks everyone needs to arrive in good time at JED, so I can't advise you to leave it to the last moment to arrive, but once airside there's not much to do.