If they're single-pane windows but in decent shape, exterior storms would cut that heat loss in half for significantly less money than brand new windows. A storm + single-pane has better performance than bottom-of-the-line insulated-glass windows. If there's money in the budget for better windows, that's a whole other issue to decide.
I assume the above-grade 1" insulation inside & out on the block is some type of foam? (Pink, blue yellow, white, ???) Assuming its the cheap stuff (white EPS) you have clear wall values of about R8. It's XPS it's ~ R10, if it's iso you have ~R12, so you're starting in the range of a 2x4 studwall with R8-R11 batts on R-values, which isn't great, but better than nothing.
Below grade in the basement you have nothing?
And in the attic...???
Depending on how thick you can make the wall you can either go with EPS (R4/inch) XPS (R5/inch) or polyisocynaurate (R6/inch). EPS is cheapest per unit R value and can be bought in varying thickness with/without facers, etc. Glue it in place directly to the older exterior foam with foam-board adhesive, seal all of the seams with 1-part spray foam for a near-perfect air- barrier. (If using multiple layers, stagger the seams for even better air barrier characteristics.) Though-screw vertical furring strips into the block wall as you go for mounting the siding, which leaves a rainscreen/drain-plane gap keep bulk water from weather penetration out of the wall assembly.
Depending on your climate the type & condition of the interior insulation & wall finishes, and total R-value you may or may not want to use facers on the new exterior insulation. While masonry walls are fairly moisture tolerant, creating a moisture trap with vapor retarders can end up rotting rafter & joist ends where they meet the masonry. It's better if it can be designed to dry, but whether it's best to set it up to dry toward the exterior or interior depends on the above factors.
Below grade heat loss can be huge- insulating the basement walls with at least R10 of vapor-permeable rigid foam is a good idea. With unfaced EPS you can go ridiculously thick without risk of trapping ground moisture in the wall, but with XPS you can only go ~2" thick. With iso you need to use fiber-faced (not the more commonly seen foil facer types), which is highly permeable. Don't use a studwall & fiberglass without at least 1" of XPS between the studwall and the basement wall, and use unfaced batting if you do or the studwall will rot. At 1" XPS is a weak vapor retarder, which is preferable to highly permeable foam when used in combination with a studwall, since it slows down ground moisture vapor but still allows the foundation wall to dry toward the interior (which basement walls MUST do.) It's usually less work to glue & furring-strip rigid to the foundation wall (horizontal or vertically) similar to the exterior insulation recommendation, which gives you something to hang the code-required 1/2" gypsum wallboard on for a thermal barrier between the room & foam in a fire situation. Even just insulating upper half of the basement wall is huge- up to 75% of the heat loss through foundation walls is through the above frost-line portion. (Insulating my basement with ~R20/3" fiber-faced iso reduced my total heating bill by 20%.)
Last, not least, do the ducts for the furnace run in the basement, or are some in the attic? Are the seams & joints sealed with mastic? Are the ducts (particularly the supply ducts) insulated? Typical duct losses to unconditioned/semi-conditioned space is typically 15-25% of the total air volume in older systems. Sealing, then insulating the ducts to at least R6 can be make-it-or-break-it when the furnace is perfectly "right-sized" for the heating load. But unless your house is in a very cold climate or has huge air leakage (which it might), an 80K furnace is probably 1.5-2x oversized for your house, assuming R10 insulation and single-pane windows, R20 in the attic. (I have a slightly bigger not super-tight 2x4 stick built antique of a house with known gaps in the insulation, and at -5F it's total heat load is ~30KBTU/hr- less than half what a 80K 80%AFUE furnace puts out. Before insulating the basement it was ~35-38KBTU/hr at -5F still well under the 64K output of your furnace.)
What's in the attic? Is it air tight with respect to the conditioned space below or is it a Swiss cheese of recessed lighting cans, plumbing & flue chases, electrical penetrations, mouse ladders & etc? Air sealing the attic/conditioned space boundary is hugely important, and often difficult to do as a retrofit. Foam-insulating the roof deck from below, sealing off the attic vents to convert the attic into an air-tight conditioned space is often an easier/better way to go in an existing home.
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