With modern gravel bikes (especially on big tyres) it's easy to find their limits abruptly as they're so comfortable on flowy stuff. Easy to forget they don't have the travel/compliance to take the really rough stuff at speed so hit a lumpy section too fast and all you can do is try to float through and hope for the best... or bail.
As for pedals, I've used single-sided SPDs on cross and gravel bikes for years. Great for hopping on the bike in normal shoes but even better on sketchy/slidy sections where you're better being unclipped, especially if the bike's loaded up. EH500s are the faves (improvement on A530s due to grip from the pins), albeit with added shin-shredding potential on the flat side.
Can sympathise with your SPD-induced off as still remember riding to school on early SPDs when I was still training, slowing for a level crossing and just coming to a stop as I got the dreaded 'click' of doom. Cue the slow motion topple and flipped-tortoise routine in front of a load of girls from the all-girls school round the corner! They enjoyed it; me, not so much. Youthful blushes and all that.