As minibutmany stated, if you've already coded a fair amount of the game then you will be spending alot of time not only merging your application into Unity, but also learning Unity and C#. If you feel that the time it will take to do all that is worth the outcome then by all means use Unity.
And as I said earlier, unless you buy the pro version of Unity then you won't have all the "pretty" things it offers such as realtime shadows or render targets. See here.
Also, Ogre has a pretty good community that are often happy to help.