Major issues are a) securing your starting point and b) securing much-needed metal. Unfortunately, the metal to the north of your base is the only field on the map. Use a crawling Falkner initially to hold off the aliens, as you´ve discovered he can´t do this indefinitely but he can do it long enough to allow you to sort your economy out. Drop a colony centre in the metal field and upgrade it with turret towers and power plants- that should secure it well enough for you to start unhindered mining operations on the metal.
Now you must quickly research the Aurora, build about seven with rockets and tell them to hold position- place them strategically like so:
Picture 1 ( http://www.mektek.net/forums/uploads/post-32-1126117709.jpg )
Notice that Falkner is lying down by the wall turret- you must keep him there to stop the aliens killing your artillery- they´ll generally attack him or the wall first. Falkner heals himself faster than the aliens can hurt him with the rocket artillery there. Make sure there are a couple of Gruzes on standby to heal the wall and keep the aliens pointlessly targeting it. Now you´ve secured your base.
The LC base is to the west, use Amursks with AA chemical rockets and Orsks with Chemical rockets to destroy it- The Amursks are necessary because of the enemy Mercuries there.
Once the base is dead drop a colony centre on its ruins and pump out Rasputins with heavy lasers, shields, repair systems and chemical armour. Also, you´ll need auroras with the artillery gun (NOT the rockets- as you know the alien structures will stop them easily). Find the saboteur to allow your tank cannons to function again. With Chemical armour, there are only a few aliens you need to worry about, namely the fat one that looks kind of elephant-like, and the defence structures that fire the orange balls.
Picture 2 ( http://www.mektek.net/forums/uploads/post-32-1126117761.jpg )
Send rasputins ahead of the artillery. When one of the orange-ball structures is found, tell your artillery to attack and pull the tanks back. If the structure fades out of viewing range before being destroyed, send a different, healthy, tank to make it visible again. The automated repair systems will handle the scratches that this method causes.
Good luck!