A verbal tic would be an action that someone repeats without wanting to which in some way affects their speech. For example if they stop all the time in the middle of words to breathe, if they smack their lips, click their tongue, or click their teeth together whenever they say a word, that type of thing. A verbal crutch would be something that is used as an aid to speaking, without necessarily getting someone all the way to speaking properly. I'm not sure if you're familiar with Japanese at all, but they have commonly taught English pronunciation through katakana (in the past and continue to do so, to some extent) which is a Japanese alphabet that has less sounds than English does. This is an example of a verbal crutch, because they adjust the sounds to be more similar to the sounds they are used to making in their language, they can speak English that is understandable to some extent, but without properly learning the new sounds. So I would say they are fairly different, from my understanding of the terms.