I like this initial response, and I think you have come up with a number of great ideas. Here are a few more ideas to help you develop this assignment and get an even better mark. You might want to develop what specifically Chris learnt from his months of solitude and how he has changed as a result. It was always his intention and dream to stay for longer in Alaska, so you need to explain fully why he chose to attempt to leave earlier. You might even have him thinking about some of the many characters he met along the way and thinking about those relationships and how important they are to him, as he realises it now.
Lastly, I would write a lot more about what Chris felt and experienced when he tries to leave and can't. Would he berate himself for not realising the impact of sping on the ice in Alaska? How would he feel? We are told later by the author of this great book that if he had a map, he would have realised that he could have crossed the river in another location, very close to where he was. Would he wish that he had taken a map? I guess that having decided to make such a big decision, and then to have that choice taken away from him, is going to make Chris feel upset, frustrated and annoyed. You need to try and capture that in his feelings.
Good luck, though! This is a great start and by considering my questions you should be able to get a good grade.