Chapter 2 answers...this shouldn't be as long.
Forts...are usually used by feudal players invading pagan lands so I don't know how useful they are to the other side! However, they are cheap, they provide an extra, if weak, layer of defence against sieges and I tend to put them in all of my own counties just to be sure.
We've already discussed this above so i don't need to go over it. What I do agree with is that it would make him a very strong vassal, but the land would be in your realm AND because of how inheritance works, his sons are going to split that land up for themselves. So essentially I wouldn't worry about it too much for now. Just get the land into your realm. You are always going to have powerful vassals but that doesn't mean they are troublesome (if they are your friend for example, especially in this case as sons break up power after death, give them all the land you want!).Also, his designated heir is none other than Svetozar, Chief of Luki and one of Rurik's vassals! Perhaps some ‘unconventional methods’ could be used to bring this province into the realm? Though the legalities and consequences would need to be examined further. Even if Sviatopolk’s convenient death could be arranged, would his county be brought under Rurik’s rule through the inheritance by his vassal? [Ed. I assume so, but being a newbie seek confirmation.] There is also the consideration of making Svetozar – already a powerful vassal – too powerful. He and Rurik are not exactly best of friends as yet!
Very, though I doubt you will have much in the way of them for a while. Other people have answered the combat question very well so I'll skip over it. Basically, get cavalry if you can but expect your armies to be made up of mostly footmen and plan accordingly (i.e. put tech into them and prepare for slow marches instead of fast campaigns...aside from raiding on boats!).[Q1: So I’m presuming that demesne and liege levies can be raised in peace time – which could then be added, for instance, to the standing army already available and used for raiding. But, given the vassal levies cannot currently be raised, these would be the only troops available for such activities for now. I tried reading up on this aspect, think I have the answer, but didn’t find anything definitive after a cursory search, including on the Wiki.]
Basically. Though keep in mind that you cant declare war with raised vassals (one of the reasons why standing armies and retinues have certain advantages, despite expenses).
[Q2: How valuable are cavalry in this time period – with a master horseman as a leader or not – and how do you go about getting them? Is it a resource-based thing? Or only available in retinues?]
Technology is researched in your captial and tends to spread outwards from it. So if that is the highest tech province and also produces the most gold and troops (and for long term planning, has the most development slots to build castles, towns etc...) pick it as your home county. Generally people pick a good duchy capital as their main capital and hold two duchy titles for themselves (the max amount a feudal ruler can hold without penalty) along with any kingdoms and empires etc. If you can get two duchies that are large and next to each other on the map, then that's the best option.[Q3: given it isn’t the home county, does this make any difference/have any benefit? Perhaps to the attributes of any levies later raised in this county?]
[Q4: My intention is not to build any more Temple holdings (the only new holding currently available) due to their expense and my uncertainty as to whether they would be worth it, for now anyway. Even in Ladoga. However, the Forts seem cheap and at face value like a very good idea for defence, including against neighbours who may have a similar idea to Rurik’s about the benefit of raiding. Would it be a good idea to commence building Forts in all the realm’s provinces? That would be my current intention unless advised otherwise.]
Forts...are usually used by feudal players invading pagan lands so I don't know how useful they are to the other side! However, they are cheap, they provide an extra, if weak, layer of defence against sieges and I tend to put them in all of my own counties just to be sure.