What kind of dealer doesn't have anywhere proper to ride? That alone tells me this was not a proper professional operation, even a dealer that focuses on the hacking and low level amateur market absolutely ought to be properly assessing and schooling their stock before they market them IMO, and I don't see how they are doing that without an arena or field they can ride in. To me the kind of dealer that sticks a saddle on, pops up and down the road a few times then declares ready for sale is the kind that has loads and loads of horses in at once, usually sourced pretty indiscriminately from Ireland or the sales or similar and raw/green as grass, selling at reasonable prices, and the profit margin comes from buying cheaply, investing very little in and moving on as quickly as possible. That's fine if you are an experienced buyer, have a good eye and want a project and to do the work yourself, so all you are paying the dealer for is effectively the hassle of going to the sales/shipping over from Ireland, but its no good for an average leisure rider who needs a 'made' horse (which is why perhaps, being charitable, this dealer has good facebook reviews, they may be from a totally different kind of buyer to you or they may be fake ).
Re the spooking, very very few horses, even the totally bombproof saints are completely 100% spook proof, horses are flight animals after all and something can always happen to startle them no matter the skill of the rider. I think anyone looking to own their own horse, novice or not, does need to be able to sit and work through an occasional minor spook (talking a sudden halt, snort, perhaps back off or swing sideways suspiciously kind of spook, not a bolt/bronc mad panic episode). So I suppose it's just possible the dealer was being honest in his description of the horse and it was just unlucky that this was the day there were demons in the verges or the horse was feeling particularly fresh or whatever. Or (perhaps more likely!) the dealer was unscrupulous and just looking to make a quick sale - although a truly bad dealer knowing he had a novice come to view would have drilled the horse on the lunge or up and down the road for a hour or 2 beforehand so it was too knackered to spook, or even kept it away from water or dosed it up on sedatives beforehand, these things are more common than we like to think sadly - I suspect he was just a bit casual in his assessment of what's suitable for a novice, hadn't really tried the horse properly and/or has so many horses going through his hands he can't remember which is which!
OP it's super frustrating buying a horse at the best of time what with dodgy dealers, time wasters, idiots that can't measure their horses properly or know when it's hopping lame etc etc, and things are a bit madder than usual out there at the moment. Plus winter is not typically a great time to buy, I know it's annoying but I'd take your time, ideally you'd buy privately or through a dealer that has actual recommendations from people you know who have the kind of horse you want (contrary to popular opinion there are still out there some excellent dealers who really put the work in sourcing animals truly suitable for novices and leisure riders, putting miles on the clock and ironing out any issues or training problems, but quite rightly this takes time and expertise just as much as training competition horses does, so they do charge a premium which a lot of people feel unwilling to pay when "all they want is a happy hack" or similar). Can you ask your instructor and people at the yard for any recommendations and to keep their ears open through the network for anyone looking to sell?