Okay, fisrt you only side b once... While I dont think that it should be spammed, it is useful in getting your opponent in the air for some fair bair ****. Also, it tacks on 20 percent or more depending on how much you use it. I use it but rarely for the bowsercide. Also, you often walked in as an aproach which isn't the best option. Short hop a fair or infinite jump side b(sometime it works). I'll even run in and upb sometimes because it goes through or clanks with almost everything. Go in and then go out before the move ends so you dont get punished if you miss. Dont dair with bowser hardly if ever... its just not a great move. Fire breath is also a wonderful shorthopped aproach and you can even use it defensively or as an edgeguard. Upb out of shield is the biggest thing. It is a very fast high priority option for bowser to use and you neglected it. Had the shiek been in proper position at the end you would have lost... Good start though and keep at it.