1. What it take to get a job as Level Designer at Major Company, like Crytek ?
Numerous things really, a good starting point though is a strong portfolio, showing willingness to learn and improve. Luck is part of it - to get your foot in the door of the industry is normally the big step. In my case Codemasters just happened to be looking for graduate level designers when I came out of uni. Once I was there and built up a few years of industry experience I was able to transfer across to Crytek. I know one guy who took a different route though, who applied at the indie/student games studios after university, and worked his way through those for a few years until he got his shot working for Headstrong in London and now Ubisoft.
I've said it before, but I think it's important that whilst at university you don't do the bare minimum that they ask you to do. Lots of people on my course did that, and when they graduated they all had the same model of the same castle on their portfolio which they'd been asked to do for the 3D side of the course. Just because you get good grades doesn't mean you have learnt all you need to. In my final year group project in my team of 10 people, some of us spent months building levels, programming and modelling, and a couple of guys basically added in a few drawings in the last week. We all got the same mark and everyone got a 1st, as it was poorly tutored, but really, I know who got the most out of it.
I spent a lot of time working outside of my coursework though, learning before it was taught and building up my portfolio separate to my uni work, which I think helped me in the long run. Experiment with modelling too (which I can see you have) - some companies use 3D modelling packages to create levels rather than in-house editors. Experiment with different engines, so you are able to compare the strengths and weaknesses of each.
In terms of the degree itself, I don't think it's as important nowadays if your portfolio is strong enough, but what a good degree does show is a commitment to your desired position, so aim high there too. If you're not involved in any mods, have a look for something you could jump into as a side project as well - always helps to get experience working within any kind of team when it comes to design, whether they are industry professionals or not.
2. Do you think my Portfolio is good enough to get that position ?
It's not really for me to say, but what I would advise you to do is check out this thread:
Flick through the portfolios in there. Yes, many of them contain industry work but you'll normally be able to see what the person was up to before they got their break. Compare their work to yours, both pre and post working in the industry, and ask yourself does yours actually compare? If not, what can you do to improve yours? What are they showcasing that you'd be able to learn and also show? The best thing here is to very critical about your own work, don't be defensive, it's probably one of the worst traits a designer can have when it comes to their work. No one produces anything perfect, there's always room for improvement, and you will get criticism of your work, especially when starting out professionally.
Get your degree whilst doing as much personal work to improve your skills as possible, write your CV based around your achievements thus far as a designer (no one in the industry needs to know someone used to work in Sainsbury's), write a covering letter for each company you apply to, detailing exactly why you would like to work for that company and what you can bring to them, and get your applications out there. Finally, it's good to realise that many companies hiring out of university know that the candidates need training and have no experience. Don't make the mistake of approaching your application as 'the best level designer ever', even if you think you're awesome. When I interviewed at Codemasters I literally said to the guys that what I wanted was just to be given the chance to work with such an established team, and to learn as much as I could from them, I think that resonated with them much more than someone coming in assuming they were already the dogs bollocks, so to speak.
Good luck!
I created my own version of the Southfield over the road during my time at uni...anyway, agreed with Chris, best to take inspirational elements from these real world places and combine them with fictional set pieces to ensure you cater for gameplay as much as possible, keep it up 
