What kcodyjr said but for different reasons. A zone with only 20' of baseboard is guaranteed to short-cycle that boiler. Baseboard is cheap- 50' still wouldn't balance but would be more likely to run long enough to overlap with a call for heat from another zone, all of which are apparently under 60' anyway. At 162' total it still comes in at 524 BTU/ft with all three zones calling for heat, so it won't require any tweaking of the near-boiler plumbing to protect against return water that is too cool.
As configured any single zone can only emit about a third of the boiler output, which isn't the greatest way to run the boiler. With three zones of 50-60 feet it pretty much balances when all zones are calling for heat. But a 20' zone can't even emit 1/5th of the boiler output, and will cycle quite a bit when it's the only zone calling for heat.
There seems to be a lot of gaps & compressions on the above-grade fiberglass, which is going to cut into it's performance fairly severely. Tuck them in at the corners & edges, then tug gently until it's just proud of the stud edges so you get a complete fill- it' makes a difference.
And lose the poly sheeting. The ubiquitous use of 6-mil poly has been the cause of more problems than it ever solved in a MA US climate-zone 5 location. Air-tightness is more critical than vapor-tightness for controlling wintertime moisture adsorption at the sheathing, and if you seal the wallboard carefully (foam the back side of any electrical outlets with can-foam, and caulk the front side to the wallboard, and caulk the wall board edges to the framing), you won't have a significant mold risk at the sheathing even running with no interior side vapor retarder. If you have vinyl siding you can call it "done", and be fully code-compliant, since vinyl siding is inherently back vented, and the sheathing passes through at least some of the winter moisture load during the winter, and dries quickly when it warms up. With vinyl siding it meets the "Vented cladding over wood structural panels" prescriptive for [URL="http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_7_sec002_par025.htm" US climate zone 5[/URL] (which is all of MA), and that allows you use standard latex paint as the interior vapor retarder (3-5 perms), which has significant drying capacity for purging any moisture that finds it's way into the assembly, making it far more resilient to moisture drives from either the interior or exterior.
If you have a less-vented siding type, to meet the full letter of code you can paint the wallboard with a "vapor barrier" latex, which is about 0.4-0.5 perms, which is about the same permeance of the kraft facers, and is the middle range of a Class-II vapor retardency, yet still provides an order of magnitude faster drying rate than 6 mil polyethylene. (What takes a full season to dry through poly can pass in a week with vapor-barrier latex.) Only if you lived in northern Quebec or the cooler parts of the Canadian midwest would poly vapor retarders be of more help more than harm.
On the below grade lower-wall section you'd be better off with the kraft facers on the cool side of the assembly since as-installed they impeded the drying of ground moisture into the room, trapping the framing in the damp. If you slip in an inch or two of foil or vinyl faced rigid foam between the concrete and studs and re-install the batts with the fiberglass in contact with the rigid foam the kraft facers will be OK. If you go with unfaced EPS, unfaced batts thick enough to contact both the foam and the wallboard in a compression fit would be much better. (Unfaced type-II EPS is about 1.5 perms at 2".)
Hopefully you stuffed some backer-rod in around the window framing gaps and sealed it with a low-expansion foam before stuffing the fiberglass in? Here too a full cavity fill is important to limit the thermal bridging. With the exterior side foam-sealed stuffing those skinny cavities with fiberglass completely with a compression fit. You want to stuff it until it's about as springy as an R13 batt or a little bit denser- nowhere near as loose as an uncompressed R19. When you compress it a bit tighter than an 13 it's R value rises to about R4 per inch, whereas with gaps and low density you'd be lucky to see R2/inch.