I am afraid of you (phoboumai humas). He shudders to think of it.
Lest by any means I have bestowed labour upon you in vain (mē pōs eikēi kekopiaka eis humas). Usual construction after a verb of fearing about what has actually happened (mē pōs and the perfect active indicative of kopiaō, to toil wearily). A fear about the future would be expressed by the subjunctive. Paul fears that the worst has happened.