One tank is a huge target which will just be blown up, it will the target of all the antitank shots.
90 boyz is more than enough, and that number just about fits on the table top
The warboss should have an attack squig and cyborg body, both are great upgrades. Also the warboss is a bit of luxury.
So drop the 20 boyz and battlewagon.
So let's talk about antitank. A few rockets are not enough at BS2. Also you can not hope the enemy will let you walk about and klaw tanks. Maybe consider one of the following which ever takes your fancy.
9 Kannons with ammo runts.
9 Kanz with rockets.
3 buzzsaw+rocket koptas.
More deffguns. At the moment I would have them in 3 squads of 5 so you can target three targets instead of one, big numbers are good to get the squad to be fearless.
The original list has 128 models at 1500 pts

, they can not kill them all, unless it is a Crowe list. If it is a Crowe list just give up, you are able to beat them but just do not put yourself through it.