It’s not really that complicated - don’t be discouraged! It seems to me that you’re to eager to translate into English, when you should be trying to read the Greek. The idiom here is not “it seems to me” but “we seem to me” (=it seems to me that we).
καὶ γὰρ οὐδὲ πόρρω δοκοῦμέν μοι αὐτοῦ καθῆσθαι.
“For we seem to me to be sitting not far from him” → “For it seems to me that we are encamped not far from him”
Yes δοκοῦμέν is a personal form of δοκεω not an impersonal form like δοκει, εδοξε, or δεδοκται (see also CGCG 36.4 for more on impersonal constructions). As Paul indicates, only impersonal forms of δοκεω can be translated “it seems/seemed” while a personal form like δοκοῦμέν has to be translated as “we seem”.
Ah - yes, of course. I really should have known that. I think I’m getting better at thinking in Greek - and avoiding as much “English Interference” as possible - but there are times when I’m simply trapped and can’t extricate myself.
Many thanks to Mitch and Paul for your rapid and most helpful responses - much appreciated. - Fred