Has anybody noticed that almost every British manga/anime character has something to do or is at least related with demons and monsters. Not joking here's a list; Jack Simons - Darker than Black Ciel Phantomhive - Black Butler Integra - Hellsing Oz (debatable) - Pandora Hearts McDowell - Nigma Allen Walker (yes he is actually British) - D.grey-man Alice - Alice in the Country of Hearts L (yes he is actually British) - Death Note Howl - Howl's Moving Castle & Bakura - Yu-Gi-OH
Alucard is Dracula, the codename alucard was given to him after abraham van helsing beat him into submission, and enlisted him into the hellsing anti vampire program. Once all restrictions are removed he returns to his original form, which is that of Vlad Tepes.
As said, he got beat into submission, implying that he feared for his life. If he wasn't afraid to die he propably would have just torn Abraham Hellsing in half with his bare hands without breaking a sweat, why would he otherwise have gotten locked up in the basement?
It depends on what lore you go by since there are many. The lore that Hellsing follows portrays Alcuard and Dracula as one in the same. There are also other stories about Alucard being the son of dracula or dracula's heir in general along with Dracula marrying Mina.