By the looks of it you are actually in a relatively safe place (don’t take my word for it) but the manual states the typical wattage is 8 and max is 18, so your psu should be good to 15w, use it at your own discretion, but I’d be happy at that margin ! Obviously it doesn’t look like a 1w fuse would last, so scrap that idea , 2A fuse would be great, but maybe not for a gig