Exact probability of landing the rate-up 6★ with your current savings. Models soft pity from pull 66, the 50/50, carry-over pity, and the 120-pull spark.
Only if you're comfortable losing the 50/50 and walking away. The spark doesn't carry over, so stopping at 100 pulls with no featured unit means the whole chase resets. The classic rule holds: don't pull unless you can afford the worst case.
Your 80-pull 6★ pity counter carries over between limited banners. The 120 spark does not. Weapon banner (Arsenal Issue) pity never carries over.
Arsenal Issue guarantees a 6★ weapon within 40 pulls and the featured weapon by 80, but the featured rate is only 25% per 6★. Signature weapons add roughly 25–30% damage — strong, but luxury. Characters first.