8 weeks is a long time, you've got plenty of time to turn this around. If you can, I'd recommend signing up to snaprevise, they're short videos which explain chemistry and have good worked examples. This might be a weird bit of advice, but I jumped up a grade by attempting the paper backwards, might be worth a try. As for the 0 uni offers, you can always apply again next year or go through clearing, plenty of universities are scouting out students to fill their spaces after results day. Also, it might be worth reading the mark scheme for your mock, sometimes the wording of an answer can make or break you, so improving by a grade might be possible if you know what the examiner is looking for (key words). Don't give up.