The Dracula thing is easily explainable. He could have just faked his death like in Adventure. It's lame, but he did it once already, and this way Trevor is still the first to kill him.
The age thing is an easy fix also. Have Alucard born in 1432, that would make him 18 in Legends. This way, when he goes into hibernation until CV3, he still has that teenager mentality Iga wants him to have and it would still make him about 400 years old like SotN says.
Then there's Lisa. Let's say she was 18 when she had Alucard and she dies when she's 30. That would put her birth at 1414 and her death at 1444. When Dracula finds out she died he curses humanity and declares war.
1414 -Lisa is born.
1432 -Alucard is born to Lisa(18) and Dracula(370).
1433 -Sonia Belmont is born.
1444 -Lisa(30) is condemned to death as a witch.
1450 -CV Legends: Sonia(17), with the help of Alucard(18), defeats Dracula(388). Dracula escapes. Alucard goes into hibernation.
1476 -CV3 Dracula's Curse
It's not perfect, but it's workable and I think it's better than saying all the games fit in somehow except this one.