How do i make it so my lurker will not accidentally attack my teammates Units when i am attacking an enemy through splash...?

There's not really a way to prevent teamsplash.

But you can always center a location on the lurker in question and temporary give the lurker to a neutral player if enemies and allies are in that location. Give it back as soon as either all allies or enemies have left the location. This will stop the lurker from shooting, so this is probably not what you want, but it's the only workaround I can think of.

Impossible. Splash damage isn't something you can change with triggers.

You could flash invincibility for your allies. It wouldn't stop it, but it could reduce the damage.
Realistically, though, if you cast a spell that made a whole bunch of spikes come out of the ground, I think if your allies weren't careful, they could get hurt too.