Help for a new GM - my players are thrashing me. Options

[Opti]

My shaman player continually summons a force 4 air spirit and uses engulf on everything. It uses the air engulf which bypasses armor, and does a crap-ton of stun damage. Nearly everything except boss-types fall easily within the first round since they automatically take damage again on thier action phase, and cant do anything until they escape. Are we playing this wrong, or is there something I should be doing to remedy this?

Another of my players wants to create and sell spell formula for foci and sell them to his talismonger contact. He created a force 4 power focus (it took 4 days) and now wants to sell it (according to the rules for fencing to contacts) for 18,000 (foci power (4)x 18,000 = 72,000, and sold for 5% x loyalty rating (5) = 18,000) nuyen. I went step-by-step and this seems legit, but also seems like a cheap way to get a lot of money for no real work.

Lastly, one of my players used Mob Mind in the first round of combat to make an entire street gang shoot themselves in the head, since he got 5 successes and their resist pool was only 4 dice each. Help on this stuff?

Thanks.