Here is the 'original' chronology (not original, of course, but compatible with the published Silmarillion, anyway)
FA 310 -- Bëor in Beleriand
FA 355 -- Death of Bëor
FA 369 -- Council
FA 410 -- Boromir as Lord of Ladros
FA 455 -- Dagor Bragollach
The easiest solution is to substitute Hador in not for Malach in the genealogy but for Magor. IE, have Hador born in 341. That puts him in his 20's at the Council (if we don't move the Council). Hador would have Malach's story (mostly), but would be Galdor's great-grandfather.
Obviously, we *are* making changes - not all of the dates from this list can work in our story:
310 Finrod meets Bëor
312 Haladin enter Beleriand
313 People of Marach enter Beleriand
355 Death of Bëor
369 Bereg leads some of the Edain back to the East
375 Haleth becomes chief of the Haladin
376 Haladin settle in Estolad
390 Haladin leave Estolad
410 Boromir of the House of Bëor becomes lord of Ladros in Dorthonion
416 Fingolfin gives Dorlómin to Hador
420 Death of Haleth
432 Birth of Beren
441 Birth of Húrin
443 Birth of Morwen
444 Birth of Huor
455 Dagor Bragollach
So, for instance, either we move the attack on the Stockade forward in time, or we push the Council back until later. Because the Stockade battle is happening before the Council in our version. We are preserving the order in which Tolkien introduced the Houses of the Edain to Beleriand, but not the order of these events.
So, yes, if the Council were held in FA 400, it could result in the House of Hador moving to Dor-lomin prior to the House of Bëor moving to Dorthonion. That's about the latest we could push it back. So, I would say that (as of right now) Hador needs to be born within the range of FA 341-FA 380. And his relationship to Galdor would be either grandfather or great-grandfather. The important points are that....Hador *cannot* be Galdor's father, and the Council *cannot* happen in 416 when Hador is meant to move to Dor-lomin. We are moving Hador's timeline forward. It's just a question of how much.
FA 310 -- Bëor in Beleriand
FA 355 -- Death of Bëor
FA 369 -- Council
FA 410 -- Boromir as Lord of Ladros
FA 455 -- Dagor Bragollach
The easiest solution is to substitute Hador in not for Malach in the genealogy but for Magor. IE, have Hador born in 341. That puts him in his 20's at the Council (if we don't move the Council). Hador would have Malach's story (mostly), but would be Galdor's great-grandfather.
Obviously, we *are* making changes - not all of the dates from this list can work in our story:
310 Finrod meets Bëor
312 Haladin enter Beleriand
313 People of Marach enter Beleriand
355 Death of Bëor
369 Bereg leads some of the Edain back to the East
375 Haleth becomes chief of the Haladin
376 Haladin settle in Estolad
390 Haladin leave Estolad
410 Boromir of the House of Bëor becomes lord of Ladros in Dorthonion
416 Fingolfin gives Dorlómin to Hador
420 Death of Haleth
432 Birth of Beren
441 Birth of Húrin
443 Birth of Morwen
444 Birth of Huor
455 Dagor Bragollach
So, for instance, either we move the attack on the Stockade forward in time, or we push the Council back until later. Because the Stockade battle is happening before the Council in our version. We are preserving the order in which Tolkien introduced the Houses of the Edain to Beleriand, but not the order of these events.
So, yes, if the Council were held in FA 400, it could result in the House of Hador moving to Dor-lomin prior to the House of Bëor moving to Dorthonion. That's about the latest we could push it back. So, I would say that (as of right now) Hador needs to be born within the range of FA 341-FA 380. And his relationship to Galdor would be either grandfather or great-grandfather. The important points are that....Hador *cannot* be Galdor's father, and the Council *cannot* happen in 416 when Hador is meant to move to Dor-lomin. We are moving Hador's timeline forward. It's just a question of how much.