Soph as I was telling another contributor a short time ago, because the size of your OP might discourage many potential respondents you might have had better luck placing each entry on a subsequent day, or even a second day
Q#1 We're having a barbecue next week.......?
Okay tho think I might say "(,) so can you come" or even
"…..; so, can you come…." or …. Won't you come"
No this doesn't make sense because the bbq would have already happened
No, the implication is that I have many bbq's and I'm not sure how many you have attended, whether it's your practice to avoid them
Okay but the implication is that you already knew about my impending bbq but I'm not sure whether or not you had planned to attend
Also there are besides "so" other choices for connective; eg, and, but, then, neveretheless; conveying different meanings
Yes, nevertheless, supposing you had plans out of town, might have to drive back here for the party
English is tough Soph, it must sometimes seem frustrating