The 'Glorious Tenth of August' has given Henry a great deal of prestige, in the Triple Monarchy. The Triunes' complete and utter disregard for the rights of neutrals and xenophobic tendencies is copied and pasted directly from OTL. The English kings had a lot of trouble with English privateers attacking neutral shipping and ruining their diplomacy, but the English people didn't care because it was 'dirty foreigners' being robbed. Of course, they weren't so blase when the Barbary corsairs started trolling Cornwall...
But the Triple Monarchy definitely has issues with foreign countries trusting them, and this does not help.
The Triumvirate is trying to use marriage alliances as a way of expanding influence and power, as opposed to Andreas Niketas-style conquest. It is a good idea, but one with a potential to backfire. The official name of World War I (tentatively scheduled for 1630) is the War of the Roman Succession.
Unfortunately in history, the bad guys and the jerks don't always get their comeuppance.
TTL will be no different.
The Komnenoi still in the Empire are either distant, distant cousins of the Imperial line or descended from one of Theodoros IV's or Andreas' numerous daughters. The most prominent of them is Princess Theodora Komnena Drakina, great-granddaughter of Andreas via Theodoros 'the Zookeeper' and Helena and Alexeia Drakina, great-great-granddaughters of Andreas Niketas via an illegitimate daughter he had with a camp follower from Messina.
In terms of Imperial line, male-descent, Komnenoi, one has to look outside of the Empire proper, where they rule as Despots of Egypt, Sicily (from Zoe, Andreas' favorite sister and the one present at the Black Day), Arles, and Mexico. Plus there are the Khomeini of Persia.
Word of God: If the 'Glorious Tenth of August' had not taken place and the German fleet at Bremerhaven was intact, it would have supported the Dutch. In that case, the Royal Navy would be outnumbered and outgunned and in a hard position.
From a purely military standpoint, the attack was a good idea, but not diplomatically. The closest analogy is Pearl Harbor, although the Germans aren't as incensed as the Americans. They want revenge, but not necessarily the annihilation of the Triple Monarchy (although they wouldn't mind).
Russia's setup isn't as good as it appears. The central government is weak and while Siberian revenues aren't anywhere near enough to match say Great Pronsk, the zemsky sobor doesn't have anywhere near that kind of power. Basically it has very strong regional governments, a weak central authority, and a weak king but one much better placed than the zemsky sobor to expand his power. Russia will have lots of constitutional trouble in the future.
The events along the Rhine aren't the setup for a TTL 30 Years' War. I am setting up a rough equivalent to the OTL French-English rivalry between the Triple Monarchy and the HRE. Without a Lotharingian buffer state, the two are guaranteed to bump heads.