I think it is helpful to distinguish our fundamental concepts:
1. Concept of Truth
2. Formal systems
The first concept states that we must have some concept of truth. By truth I mean that there exists a positive relationship between a proposition and the way reality actually 'is'. For example, if the 'sun is shining' is true, then what we mean by that proposition is that the sun is actually shining. This is a concept of truth that I hope we can all agree.
The second concept, a formal system, is a arrangement of axioms and rules of inference which we use to construct theorems. Logic and mathematics fall into this classification. You need a concept of truth to have a formal system. Otherwise you have no means to identify when something is true in your formal system.
The third concept, existence, is very vaguely defined concept. No one has fully agreed what it means for something to exist. For example, a materialist might say that something exist if it is actually made of particles (i.e., has a quantum wave function). A physicalist might say that something exists if it can be described in physical terms (e.g., mathematical language) and has some 'kick' observables (i.e., we may infer its existence from a related observable based on theory). A mathematician might say that something 'exists' if it can be deduced mathematically from within a particular branch of mathematics. So, there are many definitions and ideas about what it means for something to exist.
The definition that I like, and maybe I can explain why, is that existence means having causal effect to the world (either directly or indirectly) - or, being caused by something that does. For example, a photon has causal effects to electrons since they couple together. Therefore, a photon exists. God could 'exist' if he created or somehow affected the creation of the universe since he would have causal connection with our universe. We don't necessarily limit ourselves to observables (e.g., physicalism), we merely say that in principle something that has causal effects or is caused by causal effects by something that has causal effects on our world has existence (regardless if we see these effects or not).
Now, when we put all of the above concepts together we can answer some of your questions:
>>>As soon as I assume something exists, then POOF it's denoted a 1 = exists. But what if I assume something doesn't exist? Doesn't it now exist conceptualy? What value does it get? What if I assume god exists.....does he get a 1 for exists?>If I assume the universe exists then it must exist, in order for me to exist and be in the position to assume anything. ~~~Sorta has an anthropic ring to it~~~~~>But who assumed the universe existed in the first place......in order for me to get here and start assuming things?>In order for something to exist it surely must be possible, for if it were impossible it has no possibility of existing.>>So does it follow that anything that is possible must exist?Nothingness is impossible; and it was impossible for our universe NOT to exist.