1. Preoccupation with with 'solitary' activities tends to be mixed up with preference for 'seclusion', not the same thing.
2. Yes, this looks a lot like novelty seeking, the exercise of interests tends to be fleeting often competing with one thing to another, there is a fantasy thinking component to this.
3. Both, while I am cognizant I try my best to reciprocate, the lack of 'social knit' relates to emotional detachment. Interpersonal relationships tend to be marked by transience along with positive emotions. For instance person 'b' has difficulty forming bonds intrapersonally. Person 'a' connects with person 'b' and vice versa, connection is passive rather than active, since person 'b' has marked indifference, the indifference appears as anhedonia. If person 'a' were more like person 'b' there wouldn't be as much misunderstanding.
4. Yes, I would say so. I have some connections, there is mutuality that when if I ever want (as opposed to need) an interaction it's always there. They're not in my immediate social milieu but know me enough to not identify my absence with indifference or being seen as a terrible 'friend'. If person 'a' is a lot like person 'b' there is no pressure to conform or maintain connection.

Although diagnosed, I question the disorder vs traits. It is said that the success rates of schizoid disorder is very low due to due to these traits being outlined, yet there are schizoids who do quite well. As an impairment has to cause problems; work and relationships to be considered a disorder, having the traits doesn't necessarily meet the criteria of 'disorder'.

For example someone can have narcissism but this alone isn't a disorder (NPD). They intersect in terms of traits but it's not a disorder until it qualifies as something of a major problem.