Best Practice Scoping Different Scripts+Expose Object/ luabind:resume with optional return value

1. Resuming a coroutine which has yields forces me to always have a final "return 0" in my function to not produce any error e.g. consider

luabind::object m_CoroutineFunc = ...
m_CoroutineFunc.push(m_CoroutineFunc.interpreter());
lua_State * pThread = lua_tothread(m_CoroutineFunc.interpreter(), -1);
lua_pop(m_CoroutineFunc.interpreter(), 1);
int yieldTime = luabind::resume<int>(pThread);

in my coroutine i use coroutine.yield(seconds*1000) - so this value will be returned and i know when i should call luabind::resume in my c++ logic again.
However the issue arises that this forces me to always use return 0 at the end of my coroutines - otherwise "luabind::resume<int>" will throw an error which is not pretty - is there another way?

Additionally - i set this coroutine to c++ via a callback e.g. in lua i have myobj->addCoroutine(coroutine.create(myLuaFunc)) - the c++ side checks if luabind::object is (luabind::type(obj) == LUA_TTHREAD) - now for simplicity i dont want to use "coroutine.create" in lua but simply give the myLuaFunc to my callback of type LUA_TFUNCTION - how can i "convert" this function to a coroutine? e.g. LUA_TFUNCTION to LUA_TTHREAD in c++ as opposed by doing this in lua?

2. I want to create an AI engine with different scripts for each actor - lets call them actor1.lua actor2.lua - im binding my actor class with luabind - and want to expose my actor1 obj to actor1.lua and actor2 obj to actor2.lua - while only using one lua_state for everything (i think this is the best if you have many actors..)

Currently i use  luabind::globals(myLuaState)["actor"] = actor1; - for the sake of simplicity i want that every actorX.lua script simply refers to his own object as "actor" and not have a different object name for every actor - e.g. in actor1.lua i might use actor->Print("Im actor 1") and in actor2.lua i use actor->Print("Im actor 2") - how do i scope this correctly ? That once i call a function defined in lua from c++ in script actor1.lua with actor1 obj and the other time with actor2 obj and actor2.lua.

Moreover i read that by default everything in lua is global - so how do i make sure that there is no function name collision when actor1.lua defines "function OnEventX" and actor2.lua does the same ? I also like to compile these script once at startup only...

Thanks!

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