The Dutch Colonial Empire was a major colonial power in the Colonial Era. Despite Britain seizing the Cape Colony during the French Revolutionary Wars they still maintained their power to some extent. Were they not powerful enough to be able to demand land in Africa? If so, what exactly caused their decline?
I cannot answer most of your questions but what I can tell you is that the premise, "Were they not powerful enough to be able to demand land in Africa? " is incorrect. The Berlin Conference did not decide who got what but rather how the land could be divided up. But in fact the Netherlands was a signatory to the treaty and participated in the conference. I commented on a post a few months ago that explains the Berlin Conference-
At the Berlin conference, how was it decided who would colonize what?