2 children, different fathers

Hi, i'm a mother of two and both are from different fathers. I have been thinking a lot about my situation lately since it has been very hard for me. Firstly, when i gave birth to my eldest i registered my child under my surname and did not provide any of the father's information. When i tried to get a passport for my eldest, upon online registration i was asked for some information that were not in my child's birth certificate (middle name, father's info). I'm thinking that we might get the same problem in the future for other documents or IDs. Secondly, my youngest is carrying my boyfriend's surname. What if i want my child to use my surname instead and not use my boyfriend's? Lastly, me and my boyfriend broke up recently and I would like to have assurance that he would support our child. Is there any law or document i can use to ensure his support? And i would like to know if there's any law stating that he also has an obligation on me, if he has to support me in some ways too?

no child should be denied a passport if no father is listed on the birth certificate.

your second child should use the name on his birth certificate else you are creating a big headache for the future. he is entitled to support from his father, but you are not.