if my wet hand touches leather [bought in the West] or haram meat (e.g. chicken), what should I do? I cannot clean everything, so when it comes time for prayers I change my clothes and perform ablution if I have touched the above mentioned thing, is my salat fine?
If your wet hand touches meat that you know was not slaughtered according to Islamic law, then you can just wash your hand. There is no need to change your clothes. There is no need to clean everything. Only clean in cases where you are absolutely positive something has become najis, and only the parts you are certain became najis.