I would guess it will be a few weeks after 1.12 for a recommended build, possibly (probably?) longer. I just wait, use the previous version, and stalk LexManos on twitter for any updates he might spill.
Use what we got, and just keep checking back!
Java doesn't allow operator overloading, so you can't use relational operators like >= to compare non-numeric values.
Use the static equality methods in the ItemStack class to check if two ItemStacks are equal or use the getter methods to get each part of the ItemStack (e.g. ItemStack#getItem to get the Item, ItemStack#getCount to get the count/stack size).
I've seen cases of people experiencing some tps issues purely because the gui for the server is showing.
Can you try adding "nogui" without the quotation marks to the end of the batch file command and see if that helps any?