Here I am ..
My first comment on this thread is a general comment about the rules, I have not checked the situation until now. I cannot see when he opened the routes but if they were opened rather simultaneously and only to the same destinations that you fly, then I can considered it to be targeted.
But looking further, this alone isn't really enough since an airline can of course fly to any destination they wish, and very often the "list of destinations & routes" page can serve as a good hint for other airlines about potential new destinations.
Iksu airlines seems to fly to every quoted destination at maximum of the true demand, so there is no oversupply at all. Furthermore his prices are pretty much spot on with the 'suggested' prices from the system, so there's no price dumping either. And not flying with excessively big frequencies either.
So with this detailed info checked, this is still "legal", and you seem to share the markets about 50/50 in most of the routes flown by you two. But the method of his expansion rapidly (?) to most (?) of your new routes is something that I'd frown upon.
So now I am officially in red overall.. I have new planes sitting and I can't even put them in air coz I don't have $$ to set routes up.
You can get the slots even if you're in the red.
I checked also your airline and one major issue is that you're not effectively using the CRJ's capacity. You should use HD seating in my mind to fully utilize the plane's capacity on these very short sectors (pax won't mind on a short hop). In other words, you're not getting all the income you could. And the planes are brand new, thus very expensive to lease; and with rather high fuel prices regional jets are never an easy way. Actually if you check your competition, he is using ATR 72, which carries about 68 pax, while your CRJ has 75 seats (could have 85-90!). But I guess you are using 30-50% more fuel? Having C class seats is an advantage though and brings in much money.