Can I seal basement vent?

Currently pondering the best way to better insulate my attic. Live in NW, PA in a house built in the 1970s. Have a high eff furnace and ac unit. My guess is Attic is insulated with 6" fiberglass currently. Vents in the roof and sofit (though not as much as it should be). Attic area is accessible with pull down door/folding stairs. When home was inspected inspector suggested adding more insulation and having better ventilation. Currently attic is used for storage about 1/3rd of it the rest is open and unused, not high enough to stand in but enough room to crawl around in easily. Roof shape is side gabled and i would say low to normal slope. Getting icicles for sure and ice damns since the addition of gutters with leafguard. Rather not give up leaf guard since our gutters would require cleaning a lot. So far had two contractors come out and give ideas. Everyone say's it would be easy to do if we didn't want to use it as storage, just blow in insulation and up the ventilation but we want that storage area and their isn't enough space to build a raised floor area. So the suggestions have been - 1) Frame off directly near attic stairs and blow in insulation everywhere else. 2) Spray Foam (open cell .5lb) around 5.5 inches covering the underside roof and rafters and pretty much seal off the attic making a condition space. (one uses SEALECTION 500) The second solution sounds better but costs a bit more and I have read there could be issues with - Smell, moisture/breathing issues, and possible heat of the shingles. I'm a novice at this and the more reading I do the more confused I am getting so any suggestions or advice?

In pulling down some outdated wood paneling, I found that the entire house was covered this way on all the walls facing the exterior of the house.. The previous owner for some reason, placed 1x3 furring strips on the first layer of 1/2 drywall and placed styrofoam to fit and then added the paneling. It was a well done job and everything is really tight. Does this help in regards to insulation value? I am planning to replace the paneling with another layer of 1/2" drywall over the exising foam if this will increase the R value. I have poked small holes thru the first layer of drywall and it appears that there is batt insulation. Thanks for all the help...