Hey ,Louisa,will xia yuhe 夏雨荷be a good name for you ?xia(family name ) means summer,yu means rain ,he means loutus ,which symbolises the great personality and elegance  in many Chinese poems .Hope u like it ,the tone combination of your given name is 32.

For the sentence you gave ,"stick to " here means u continue with your diet without changing it or giving it up. If you stick to something, you continue doing, using, saying, or talking about it, rather than changing to something else.

不可以，至上前面一般只加名词，表示比其他的东西更重要，例如友谊至上，爱情至上等，你可以说“足球至上”，单独成句，或者在前面加，对于XX人（我，你，他们等）而言/来说，XX至上。