Once per turn: You can target 1 DARK Machine monster you control and 1 face-up card your opponent controls; destroy them. If a monster you control that was originally a DARK Machine destroys an opponent's monster(s) by battle or card effect and sends it to the GY: You can inflict damage to your opponent equal to half the original ATK of 1 of those monster(s) destroyed and sent to the GY. You can only use this effect of "BM-4 Blast Spider" once per turn.
Fusilier Dragon can be Normal Summoned with no tribute. You can then destroy him along with an opponent’s card with BM-4 Blast Spider’s effect. Since Blast Spider considers the original attack stat of the monster, your opponent will be receiving 1400 burn damage.
BM-4 Blast Spider combos perfectly with Desperado Barrel Dragon. Normal Summon BM-4 Blast Spider and target itself with the removal effect. Because BM-4 Blast Spider is a DARK Machine monster, you can Special Summon Desperado Barrel Dragon once he is destroyed.
Treacherous is much more of a problem than Desperado is. It's splashable, and is less telegraphed. (Can still be relatively easily discerned, but you'll see Desperado coming from a mile away, so it's still a notable difference.)
Target itself to pop both itself and opponent's card, then special summon Desperado Barrel.