[SumireSatoh]

Don't mention. I'm glad to hear I could be of any help.
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5.) 彼の間合いのギリギリを頭に叩き込みなさい!

They run into a group of people protecting the target.

So would this be something like?:
"Get it into your head he is not at the right distance!"
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So, the word 「彼」here indicates the 'target', am I right? The sentence itself「彼の間合いのギリギリを叩き込みなさい」sounds a little awkward to me, not grammatically perfect at least. Something might be left out after 'ぎりぎり'.... anyway I think it could be「彼のギリギリの間合いを頭に叩き込みなさい」(here you can see a little difference in its word order.) , which means「彼の[動きの]正確なタイミングを頭に叩き込みなさい」,「彼の[動きの]タイミング（＝間の取り方）を正確に頭に叩き込みなさ い」or something like that.

My sentence might be awkward but I think it can be like:
'Get into your head the exact timing of his motion/movements'

27.)
今後はこのメンバーで活動するんだからしっかりとコミ ュニケーションは取ること！
Take the communication well in future because I am active with this member!
The whining person is now angry because some one made fun of his English.
"Because I have to deal with this member we should learn how to communicate better in the future!"
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The subject for the verb 活動するis 'you,' the hearers, or 'we,' the hearers and the speaker.
'From now on you/we all are going/supposed to work as regular members of this team. So you should learn to communicate with each other more effectively/without failure.'

Sorry my sentences may be awkward and explanatory so you may have to put them to more natural, better expressions.