C++ integration / DSEL alternative questions

[Moose <moose@...>]

Hello Lua Community,

I am maintaining an existing C++ application that features, in a core 
library of it, an embedded C++ DSEL (written inlined in boost spirit) to 
execute user defined tasks. Those tasks call functions in the library 
itself. I would like to evaluate Lua as an optional alternative to the 
embedded DSEL, while keeping the architecture itself intact.

About this, I have a few questions:

1) Can Lua scripts call functions in the very same DLL that calls the 
interpreter?

For my experiments I have used LuaJit with FFI binding. Successful so 
far, but i noticed I have to load the DLL inside the Lua script 
specifically before I can use it. In my case, that would imply the DLL 
that executes the script would (via script) load itself and exist twice. 
Or indeed many times as there are lots of those scripts.
This is what I have to avoid. I have a number of objects already 
present at the time the script gets executed and I would have to access 
those objects rather than create new ones. Is this possible, with 
LunaWrapper for example? Even a singleton would exist twice in that 
scenario.

2) When LunaWrapping existing classes, is there a standard pattern or 
best practice for doing so? Like, I have an object and want to call 
multiple scripts that use it. Do I create a wrapper class that derives 
from the existing class and somehow pass it into the scripts? Or is it 
better to modify the existing class with the LunaWrapping boilerplate?

3) Can multiple Lua States coexist nicely?

4) In a real world use case my users have many scripts in my DSEL that 
get executed at a frequency of about 30 Hz or more. Would I create a Lua 
state and execute the chunk every time or can I re-use the state after 
instantiating it once and excecute many times?

As you can see, I am a Lua newbie and just hope to get some answers in 
order to get a grip on the question if Lua is a suitable alternative for 
the DSEL scripts. Any hints are appreciated.

Thanks,
Moose