First thing first, add the following to the start of your batch file:
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1

Now, you need to understand that the number of threads you should be using is dictated by your card (not all cards can run well with 1 thread same as not all cards can run well with 2 threads) so find out which is best for your card (by finding out I mean try it out for yourself).
Next, the number of TC (thread-concurrency) in your settings is capped by how many threads you're using and by how much RAM you got in your system (to determine how much TC you need to set: Shaders*n+1 (this formula will give you, generally speaking, the best resaults), n can and will be any number you choose but is subject to the limits of your cards/settings, although YMMV).

So, for your OP, if with 1 thread you see low KH/s than you should change your TC.

If with 2 threads you still get error -5 (after adding the setx commands) than you should lower your TC. A common TC value that works well with -g 2 is 8193.

Also note that with 2 threads and lower TC you might also need to lower your intensity, although with your card I'm not sure of it, but keep that in mind.