'Tho' is not a word in its own right: it is nothing more than an abbreviation of the word 'though'. People who can't be bothered to write the six-letter word 'though' write the three-letter word 'tho' instead. It's similar to writing 'thru' instead of 'through' - a lazy shorthand.
And yes, you can use 'though' at the end of the sentence to show a different opinion. Putting 'though' at the end of a sentence is just the same as putting 'but' at the beginning or in the middle of it. For example:
The film is good, but it's rather long = The film is good. It's rather long, though.
He's a bright student, but he's a bit lazy. = He's a bright student. He's a bit lazy, though.
I wouldn't recommend writing the abbreviation 'tho'. The proper spelling is 'though', so that's what you should use.