Everything in aviation takes longer than you think it will.....
Your schedule, although possibly achievable is un-realistic, you are putting undue pressure on yourself, and in the rush to get things done could end up causing more delay. A rushed exam/test when you are not quite ready is an expensive and demoralising experience.
Keep speaking to the people who have made the job offer, let then know you are trying your best to keep things on track, but that certain things are out of your control.... They maybe able to cut you some slack.
We have two students at our school, who have come to finish off ppl's started in the US. Reasons - Weather, lack of instructor, lack of aircraft etc etc etc...