I have found that the only use for old LME is making starters, but at 3 years since purchase yours may be too old even for that. I was using old LME for starters for a while, but I found that as it aged it became less fermentable and thus didn't give the yeast growth I wanted.
When I combine the cost savings of buying grain in bulk and using a little less grain due to better control of my crush, and thus my efficiency, I calculated that my mill paid for itself after 22 batches of beer. If you are brewing biweekly then a cereal killer type mill can pay for itself in...
Ok then, to get higher ABV you will have to boil that sap down quite a bit before fermenting it. If you don't already have a hydrometer you should get one and learn how to use it. If you are new to fermenting then I would suggest starting with a lower gravity, something like 1.050. I don't know...
Just to be clear, are you fermenting straight sap or sap that has been boiled down as you would with maple sap? Alcohol content is of course related to sugar concentration, so a higher ABV would require a higher sugar concentration in the liquid you are fermenting.
Just listened to this and I really enjoyed it. My eldest son turns 18 (legal drinkingage here) a year from now and I had been toying with the idea of brewing him a mead for his birthday, now I know that I want to do this.
When I open a sack I transfer the grain to buckets for storage, to make it eadier to pour I only cut one corner (with sharp scissors) which minimizes the amount of plastic that can fall into the grain.
A good thermometer is worth its weight in gold. The thermapen is top notch, but pricey. I use the Javelin thermometer, I consistently get stable readings in 4 seconds, at about a third of the price of the thermapen. https://www.amazon.com/dp/B00GRFHXVQ/?tag=skimlinks_replacement-20
If the gel is petroleum based it may be slowly eating through the plastic on the probe cord, it wouldn't take a very big hole for some gel to get in and foul your probe.