1.thank you for you continued help,without which i can't do well in my english study.
这个句子是正确的,非限制性定语从句,由于某人的帮助,用介词with/without
2.the twentieth teachers' day is coming,i wish you happy and success in everything
这个句子前半句正确,wish sb.+名词 = wish sb.be动词+形容词,所以应该改为 i wish you happiness and success in everything
也可以改为 i wish you are happy and successfull in everything
类似的有：Wish you a good luck