Epsom salts contain magnesium.
this will penetrate the skin and enter the body, mostly where the soak occurs.

Magnesium has been found to be very deficient in the US. Estimates are 70% of people do not get the RDA of it 400mg for adults, or are losing it quickly thru the urine, diabetics, diuretics, alcohol, caffeine.

Foods high in magnesium are on that thread.
You can look up foods that you commonly eat on this website to see how much magnesium you actually consume:
http://nutritiondata.self.com/
Pay attention to the serving sizes in the upper left of each page, so you can figure out your magnesium intake. That site is very interesting and shows many things you can profit by. The inflammatory index is also useful...you want to limit inflammatory foods.

You can choose any chelate-- glycinate, gluconate, malate or citrate. Target 200mg elemental a day to start which is 1/2 the RDA for adults. I explain "elemental" on that thread.
Many supplements do not give elemental on the label. You might have to look that up.
For example a 1000mg magnesium malate has about 150mg of elemental magnesium in it. The rest is the malate portion

I think you should start here, because of your diabetes, and poor circulation.

I also think you should have thyroid testing to see if your body temperature is low, due to low thyroid. When you get that testing done soon, also ask for B12 test and Vit D.
Diabetics can be low in Vit D often as well.
Bring your numbers here because doctors do not interpret the B12 and Vit D tests accurately in this country, commonly. Your B12 should be at least 400 and the D at 40-50 (in US units).
Metformin that some diabetics take will reduce B12 as a side effect. So do acid blocking drugs...for GERD/heartburn...they
prevent B12 absorption.

Do the magnesium first. That may be all you need. Get some more testing as I suggested in my first post and this one and then you can think about lipoic acid. It may be that magnesium is all you need at this point.