Timeline of Vortigern

Pre-445 AD: Gworthigern, a Welsh nobleman and brother-in-law of Custennin ap Magnus Maximus, serves as advisor to the latter.
445 AD: Custennin is killed in incursions by the Pictish and Scots. Custennin's son Constans succeeds him.
446 AD: Gworthigern kills Constans and usurps the throne of Custennin's kingdom (unsure which it should be- Pagenses or South Wales?). Ambrosius and Eutherius (later Uther), Custennin's two other sons, flee to Brittany as wards of their distant relative King Aldrien (or Budic I depending on dating of the former).
446 AD: As attacks get worse, and the Groans of the Britons go unresponded save for the Christian missionary Germanus, Britain starts to go downhill.
450 AD: An Anglian leader of Jutes called Horsa is invited to Britain. They defeat the Scots and Picts (possibly other Saxons too), and call for reinforcements. Then the traditional story goes on, Gworthigern marries Rowena, Hengest's daughter, and they start asking for more money, or the Britons start paying them less through avarice or a genuine lack of resources (or both!). They marry Rowena to Gworghigern in exchange for Ceint. Ceint defends itself but Guyrancgon is chased out and Horsa is made King of the Cantware.
The same year, because of Kent, Gworthigern's sons (except Pasgen) rise up in revolt. The eldest, Gwrthefyr Brydw Fendigaid (the Blessed, possibly by Germanus of Auxerre), is the leader.
451: Battle of Derguentid. Gwrthefyr loses.
455 AD: Horsa and Cadeyrn kill each other at the Battle of Aylesford. Known as Rithergabail.
In the same year, Ambrosius and Uther return. Ambrosius unites the Gododdin tribes and rules as their first King. With his new army, he joins Vortimer's forces.
456 AD: Battle of Lapis Tituli. Gwrthefyr wins.
457 AD: Vortimer is killed by Rowena, or else died at Lapis Tituli.
458 AD: In a battle against Gworthigern and Pasgen, Ambrosius Aurelianus is killed by the latter. This fits in to GoM's claim he died 12 years after Vortigern usurped.
In the same year, because of the death of Vortimer, the Saxons call a fake peace council in the Salisbury plains between their army and Gworthigern's entire army, 300 Britons. They slay everyone of them but one lord, who escapes, and Gworthigern himself. He is now landless, and his sons possess the split-up parts of his kingdom. He flees to his stronghold in Wales.
459 AD: Lightning strikes Gworthigern's feasting hall. The flaming thatch roof collapses on him and kills him.
465 AD: Battle of Mynyw. Uther avenges his brother's death and kills Pasgen, who has allied himself with the Irish Giallomanius and the Saxons.
Issues to adress:
Ambrosius lack of progeny, yet Gildas mentions his grandsons are Kings or at least leaders. Possibly subverted by Gildas' vague use of the word progeny, thus possibly including Ambrosius' half-brother Uther's grandsons.
Why is Cadeyrn fighting with his father at Aylesford if he was in revolt?
Conflicts: