A good place to start, for at least part of what you want, is Strickland's Anglo-Norman Warfare. I usually also recommend Gillingham's The English in the Twelfth Century. It's not so relevant to your precise interests, but it is good.

For medieval weapons and armour, an accessible general introduction to both is Edge and Paddock's Arms and Armour of the Medieval Knight, which should be available in many libraries and for not much money online. It has a wealth of information, but it is a popular work written by serious scholars, not a scholarly work itself. It is organized into chapters by centuries, but within the chapters the organization is rather free-form, which can make it maddening as a reference, and the lack of footnotes is frustrating if you want to look something up. A somewhat more focused work on armour is Claude Blair's European Armour Circa 1066-1700, which should be available through interlibrary loan in most good systems. Though over 60 years old, this is still the definitive introduction for good reason. It clearly traces the development of armour through the centuries, and does a lot to cut through Victorian anachronism and romanticism. As a description of how armour fits together, its form, it is unmatched as an overview. It is somewhat lacking in context - it tells you what armour was, but not how it is used. While this is one thing that has made it enduring, it also means that Blair's work only takes you so far. Unfortunately, I'm not aware of any books on Neatherlandish armour specifically. For swords, Oakshott's Records of the Medieval Sword is useful because it has A Lot of Swords. Oakshott was an amateur and when he veered away from describing swords he gets into scholarship that was a consensus in his own time but which hasn't held up. Records is great in no small part because it's a fairly purely descriptive work. There are a wide variety of other books on weapons and armour, but many of these are more specialized by time and place, or are from particular museums.

For knighthood and its 'institutions', Richard Kaeuper's Medieval Chivalry is a good starting point, with lots of further reading to pursue on whatever part of the subject interests you; it's also cheap and pretty readily available.

On the medieval nobility, there aren't as many easy intros. David Crouch's Birth of Nobility is probably the best and most accessible look at the various ways aristocracies were defined in the Middle Ages.

Monograph on Dutch medieval military history are few and far between. The subject is not a very popular one in academic circles.

Do you read Dutch? If so, I can point to Ronald de Graaf's Oorlog om Holland 1000-1370, a thorough military history of the origins of the county of Holland and its medieval wars.

The book is both a narrative history and a theoretical treatise on the practice of warfare in this region, with a particular focus on the role of water, both as a strategic goal (to control it) and as a means of pursuing war.

The book is based on the author's phd thesis but quite readable and well paced.

Unfortunately, due to the aforementioned lack of material on this topic, it is hard to fully evaluate its contents. I only know about many of the events treated herein from the book itself, or from cursory treatments in general histories. My instinct says the author may well be overreaching in some of his more theoretical analysis of grand strategy, but I cannot back this up.

If you don't read Dutch... Sorry, I can't help you further.