The problem is that by default labels size themselves automatically and thus your lv_obj_set_width
call isn’t working the way you’d expect. You have to change the long mode of the label to fix this.
lv_label_set_long_mode(label_mph, LV_LABEL_LONG_BREAK);
lv_obj_set_width(label_mph, 150);
lv_obj_align(label_mph, NULL, LV_ALIGN_IN_TOP_RIGHT, 0, 0);
The above code should do what you want.