It is not 'way' more difficult, but it is more poetic in a way. Both languages are very complex and are hard to learn fluently, but Ukrainian does have more to it. It has a more poetic range of words and is less commonly known, so there is a smaller opportunity of speaking with another foreigner or learner of Ukrainian to help improve, but it is a very nice language and it is definitely worth taking the time learning.
http://masterrussian.net/f42/ukrainian-russian-alphabet-diffs-3689/ This has some good information on the alphabets. I believe the alphabets are mostly similar so you should probably continue.
In English, when you refer to Dad, (or Mom) how he's called by his children, it's a proper noun, like a name, so it's capitalized "Dad." If you're talking about "my dad, your dad, his dad," etc., then it's just a noun and stays lower case. In Ukrainian, it's always lower case тато, right?