Thank you for your help! I was able to find fares on TAP Portugal, for 38 Euros each way, going from LIS to Funchal on April 4th and back to Lisbon on April 8th. Great deal on a "real" airline!
I haven't bought the SLC-LIS-SLC tickets as yet, they seem to be pricing out at around $1000 right now unless I can get out before April 1st. I will likely give myself a 1-day "cushion" on each side of the Madeira itinerary, so baggage won't be an issue.