[hardtimes]

'slushy'...I remember, but not slushy antigreeze..yikes, I think that I'd go for higher percentage,eh? When you put together really cold/thicker oil/full oil pan on any engine, I can see some real high pressure built up! Just a suggestion/thinking out loud, in same cold, I'd use 5W and lower the total quart capacity down a quart. Bet that would diminish 'leaking' somewhat, if not entirely...until warmer weather arrives!
I've always heard that the stock A oil pump has potential/capable of great pressure and with your current conditions..seems start up , with 10w, would be like challenging that pump to prove its potential. And, how about the oil heater..do you use one of those? Several years back, we spent 2 months in your state..1st time. It got my attn ...all the electrical wires leading out the grill of all manner of vehicles. Seemed like a good idea.