i once wrote that kind of letter. but it was goodby and i have not heard anything from that day on. which makes me wonder: what do you want to achieve?
things that come to my mind but im not going to wast both your and my time on writing a coherent text, so here they are:
-the flower thingys, does she love that? if no then its a bit pathetic? just wondering...
-the lion, what do you want to achieve with giving it to her? it will cause lots of pain, for her and you, if you give it to her.
-your letter is a bit "one standalone sentence. then another standalone sentence" and to be honest, it seems a bit clichee.
-see DM
-what do you think she wants?
-if i was an employer and your letter was a application, i'd not accept it, because it only shows what you can gain from accepting and not what you provide for me. its similar in relationships: nice that i can make you happy, but what about me, if i brighten up your whole world, thats nice and stuff, but my world, what about that? you say you love her, so show her you want to be with HER, not just her to be with YOU.
-finally, i have to advise against the letter thing as it is. write it, thats ok, but in the end, you need to talk to her. give her the letter and ask her to talk to you about this. a letter won't change anything, it might help, but not by itself. you want to talk with her!