I made invert sugar with more or less the same recipe (used cream of tartar instead of lemon juice, as recommended by Chef Eddy in his blog) and cooked it to 236F. Mine has crystallized quite a bit in the refrigerator, but I just melt it enough to liquefy it and go ahead and use it. Does yours stay liquid even when chilled? I wonder whether mine is OK to use or whether the crystallization has harmed it in some way. I would guess that the temp rose too far above 236 after I took it off the heat.
1kg of sugar
1g lemon juice
Cook it to 236F. Once it reaches temp just take it off the heat and cover until it cool down a bit. I would pour it in it's container before it cools down too much as it is SUPER thick and hard to get at. Just store in the fridge for up to six months. The fridge is just to keep it from crystallizing.
I use 30% less when I am substituting it for corn syrup. Hope that helps!
I don't think it is harmed in any way. Invert has about the same properties as honey (50%fructose, 50%glucose) so it behaves like honey. When honey has sat for awhile it starts to crystallize and turn hard. You did exactly what I do with honey so I think it is fine.
No, it is not liquid in the fridge! It is really hard to work with so I let it sit at room temp for a couple hours and that helps, but it is still a pain.