Great introduction to so many possibilities. As fiction does not require JKR's canon, would like to see Potter's Surprise extended with major changes. Some suggestions - very clear Bashing of Weazleys and their god Dumbledore. Look at "Harry's House" and "Order of the Murderer’s" by Broomstick_Flyer and "More Important Things" by Robst on ff. The fics named have a common theme of total removal from DDs careless and deadly influence and the magic worlds lack of common logic and commonsense. Also these fics have no great problem in dealing with Voldemort.
Even in JKRs story, DD comes over as nasty as LV - the abuse before school of Harry, the abuse of most students in the school - the lack of care and teaching of those children he is responsible for. And dont forget the Weazleys - JKR mentions it but other fic writers pick it up, ie the potions abuse.
Let Harry be counseled for his abuse, let the bonded pair learn non magical defense and offense, learn the laws of both worlds, and also receive knowledge of magic from the goblins and elves.
Please consider continue writing us a truly great fiction with such a wonderful beginning.