Have a look at
http://space-wolves-grey.blogspot.com/ It's got great advice on what units to take, how to kit them out and overall army composition if you want to play space wolves competitively.
Onto to your list, and I'll give you a few general pointers, but obviously I'm not sure to what extent you want to be competitive.
Njal generally isn't considered to be a great use of points, basically because 2 rune priests can do almost everything he can, slightly better, for less points. At this level he's definitely not worth it - he's taking up almost a 1/4 of your entire points! I'd probably just stick to a single rune priest with a chooser of the slain, and living lightning, and 1 other power of your choice. You can have another if you think you'll need it.
As to a dread they generally don't have that much synergy with a typical competitive
SW list, but he could work well here.
Your troops could be doing so much more for you, grey hunters are so awesome when loaded out correctly. I'll give you a few rules of thumb that you can apply to any
40k army. Firstly its almost always a bad idea to mix special weapons, because then 1 weapon is being wasted when you fire at a particular example. For example if you fire your meltagun at the tank, then your flamer is wasted. So think about what you want a unit to do on the battlefield and then specialize in that role - the division of labor

! Also Plasma pistols are never worth the points in my opinion.
Generally the best loadout for your grey hunter packs is:
9 Grey Hunters - 1 Meltagun, Wolf Standard
1 Wolf Gaurd Pack leader - Power fist, combi-melta
Rhino
You can reduce the size of the pack by 1 or 2 men if you want to save points, and you can add in Mark of the Wulfen if you want extra
CC punch, but its not essential in my opinion. The Wolf Gaurd pack leader adds an essential point of leadership for passing those counter attack roles, as well as an additional power fist attack compared with just giving a normal Grey Hunter a power fist. The Wolf standard is essential, increases the
CC power of a large pack of Grey Hunters exponetially, and a rhino protects your men and gets them where they need to be.
Sky claws pretty much suck, there's just no way you can make them worthwhile. I'd drop them without a doubt.
The heavy support squad isn't bad, but again you need to choose a role and stick to it - at the moment your heavy bolter guy will be wasted as most of the time you'll be firing at tanks, so simply drop him. Most people use their Long Fangs as Anti tank and give the squad all missile launchers for cheapness, but lascannons are fine (especially to deal with land raiders you sometimes see at this level). Drop the Melta bombs on the squad leader.
Overall drop Njal down for 1 or 2 Rune priests, re-work your Grey hunters and give them rhino's for mobility, drop the sky claws (and potentially the dreadnought) and perhaps add another squad of Grey Hunters or Long Fangs with missiles as they are both just that awesome - you'll find most
SW armies are built around them.
I hope that gives you a few ideas, but for a more comprehensive response I'd defo go and have a look at that blog. Its the ultimate resource.