A good 3 year old buck
I have planted conifers the last 10 years...to the tune of probably 12-15,000 of them. I have had limited success with them in my tags and willow. It is just too wet. I planted some diversity back, but it seems even too wet for black spruce to survive. Most of the success has been with the tamaracks that I planted, but that does nothing for thermal cover. Conifers have done well on some of the higher ground that I have, but it will be a few years yet before they are tall enough to have an effect. I also have some areas that I have mowed to remove the tags and willows, so it is just tall grasses, but that is in some of my wetter areas. I did it to try and provide some diversity amongst a large block of the same type of cover.You seem to have good summer cover, but there is something lacking that the deer just can't do without. I have a place way over to the east of you in Canada, and the deer all leave in the winter. Luckily a few hang around in fall, and there might be 3 or 4 deer on my 300 acres through November. I went up there once in the dead of winter, and the places that held deer were extremely tight cover in conifers. White cedar, juniper, pine, etc. made nearly impenetrable thermal cover that was completely sheltered from the wind, even when it came howling across the lake and through the open hardwoods.
Another spot deer bed in the fall was a couple acres of marshy area where they could lay in the sun. A friend hunting my property on the Ontario gun opener jumped a small buck in that marshy spot where the reeds/grasses were still standing and offering a bit of horizontal cover while allowing him to sun himself in the middle of the day. You might consider clearing out some of those humps in the swamp and planting dense conifers.
If I were you, I would take at least a couple days and scout/hunt the heck out of that 1000 acres of public land. You might find out where the deer are going and what they are attracted to. Fresh buck sign is relatively easy to spot, and will give you an idea of where bucks are hanging out and what kind of features they are relating to. Then in the future you can use that as a guide for what to add to your property. I would even think of that 1000 acres as part of my habitat plan. Get to know that property really well and use it in conjunction with your own property. Set some cameras up and learn all you can about the seasonal deer movements over the years. Certain patterns should emerge. This is definitely a long-term game. It has taken me about 5 years to get familiar with the public land that I hunt to the point where I am consistently taking deer.
I do have a few .25 acre islands of mature trees in the tags. I did lose a lot of trees last year with the high winds. I have been thinking of going in there and planting a bunch of conifers on those island. I can't say I have seen a lot of bedding on the islands with the past cover.