1. 작년 크리스마스 때, 새해 일기장으로 쓰라면서 준 선물. (What does 쓰라면서 means?) => A present (you/they/someone) gave me last Christmas time to use as the new year's diary book. * 쓰라면서 = 쓰라고 하면서 = 쓰라고 말하면서 = telling me to use it. 2. "야, 그래도 하느님이 우릴 불쌍히 여기시고 눈이라도 펑펑 인심 쓰시는구나" 재준이가 일부러 쾌활하게 웃으며 농담을 했다. (what does 여기시고 and 쓰시는구나 means?) => "Well, at least God is being so generous with the snow probably from pitying on us", 채준 joked laughing with an affectedly upbeat tone. * 여기시고 = 여기다(consider/regard/take ... as) + -시 (honorific suffix) + -고 (verb connective) -> looking on us as. * 인심 쓰시는구나 = 인심(generous deed/treat, giving treats to others) 쓰다(do, exert) + -는구나(I see/notice that ...). 3. 하지만 우울하긴 재준이도 마찬가지였으리라. (~으리라 what is this grammar pattern used for, I have never seen them before) => However, 채준 must have been feeling every bit as sad. * 마찬가지였으리라 = 마찬가지였다(past tense of 마찬가지(이)다, be the same) + -(으)리라(would/must be; would have been). 4. 그래서 우리는 장장 두 달 동안이나 그 일을 성사시키기 위해 투자해 오지 않았던가. (~던가 again I haven't seen this before. Also, I don't quite get 투자해 오지..... sentence. ) => So we've been trying everything [making all these efforts] to get this thing going for the past two long months, haven't we. * -던가? is a literary sounding question form of asking something vaguely, like to oneself, about a past event (similar to -나? -ㄹ까?). * 투자해 오다 = 투자하다(invest, put in resources/efforts) + -아/어/여 오다(have been V-ing) -> have been investing.

On no 4 that might have been 든가 instead of 던가 (common misspelling). If that is the case, then 든가 would mean choose to. That whole thing just translates to choose not to keep making investment hitherto. However if your example is followed by a question mark then it would be 던가 which is just a question about an event happened and finished in the past. The role of 오다 following a common verb is to assist that verb in the sense that whatever action it refers to it is continuing repeatedly up to the point in time where the declaration of the event being discussed