Threshold is strange group. Around 7 are normal workouts and many that should not be doable with proper ftp. (Spickard, Azurite etc). Most of the threshold group lvl 8 are basiclally not doable (3x20@102% with hard starts? Spickard +4, Huco etc). As most of the levels seems good, threshold is a group where you should be very picky and treat some of the workouts with reserve.
But yours is hard (have recently done 3x16 of this exact format) so I understand your pain 