First, call it a boiler, not a furnace. In the HVAC biz furnace refers to an air handler with a burner where the heat is delivered with hot air.
At 140F AWT with 213 square feet EDR you get about 20,000 BTU/hr out of the radiators, which balances well with the minimum fire output of of the ALP105, but it's getting very little condensing.
At 120F AWT (what you would need to hit the mid-90s for combustion efficiency) you'd be getting 11,000 BTU/hr out of the rads, which is barely more than half the min-fire output.
The thermal mass of water in the radiators can help- a lot! If it's getting 3 minute burns and only a handful of burns per hour it isn't going to destroy the efficiency or wear out the boiler. To max the efficiency you need to set it up with the return water temperature at the lowest it can be, with the flow/delta-T on the boiler still within spec, and not short cycling. With the thermal mass of the water in the system you may be just fine with 110F return water and it cycling on/off 5-6x /hr.
Start playing with the outdoor reset curve, during milder weather like this by dropping the parameter 5 (the output temp when it's warmer outside) to 80-90F or something, then go crank the thermostat up 5 degrees above the current room temp, then monitor the burn cycles and the output & return temps of the boiler as it tries to bring the house up to temp. If it's giving you consistent burns of 150 seconds or better and fewer than 10 burns/hr at effectively ZERO output from the radiators you have enough thermal mass in the system to work with. Bumping the parameter 5 temp up to 100F or 110F or something may be necessary for it to actually keep up with the load when it's in the mid-50s or so, and that will stretch the burn times a bit, and yield fewer burns per hour.
Then it's a matter of tweaking that warm-outdoors end of the curve to where the boilers water temp is high enough to just barely keep up with the load overnight. When it gets cooler outside you can then start dropping parameter 4 (the output temperature for when it's cold outside), until it DOESN'T quite keep up overnight, then nudge it up a degree or three at a time until it does. If you dial it in well enough on both ends it becomes a "set and forget" approach on the thermostat, since it won't have enough extra output from the rads to provide a fast recovery time from overnight setbacks, but the boiler will run at the highest possible efficiency to make up for it.
BTW: In a rented multi-family in MA you can still get substantial MassSave rebates on air sealing and insulation. If you cut a deal with the landlord to reimburse you for some or all of your net out of pocket, that's legal too, but if you're the person on the gas bill, you are the one initially paying the contractor and collecting the rebate (typically 75%) from the program.