How to get the insulation blower into the attic

1. You can, but there's a few issues to be aware of. First, your blown-in insulation requires space to stay "fluffy" and work well. Compressing the blown-in with batts will diminish the former's effectiveness and compromise the overall r-value.

   Secondly any vapor barrier (the paper on the roll) should be against the drywall. If you don't have a vapor barrier in place, I would address that (see this article from this answer for more info). If you do have a vapor barrier, make sure you buy unfaced (like your link), or remove the paper from your batts before installing.

   Your best value will likely be buying more blown-in insulation. If you buy a reasonable amount most of the big box stores will let you rent the machine for free. It is a messy two person job, however.

2. It looks like you have standard 2x4s on the edges where the drywall is attached, you could staple faced fiberglass batts to it. Measure between the "studs" and buy a roll that you can cut to width. I've seen skylights both with and without insulation, I don't know if there is a downside to insulating them.

Edit

If you put plywood over the cellulose, you're going to have a similar compression problem. This table shows you what kind of r-value you can get per inch. So the depth of your joists (they didn't look very tall) is going to limit the r-value you can get if you're covering the joists with plywood. Since it appears the insulation you already have is near the top, you won't see a huge gain in efficiency if you add just another inch or two of blown insulation. You might try asking another question once you figure out what r-value you have and what r-value you'd like to have. If you're near the recommended r-value for your climate and your house is still too cold, you might be better served by looking for air leaks first.

I own a cape with two finished bedrooms upstairs. We have knee-walls like you, as well as a cap space above the rooms (your upper attic).

We had both the crawl spaces (lower attic) and cap insulated. At the time, we were told there are two types of attic insulation: hot roof and cold roof. In a hot roof, the insulation is attached against the roof between the rafters and the air in the attic is considered warm. On a cold roof, the floor of the attic is insulated, making a warm ceiling, and ventilation and circulation occur in the attic itself (air comes in through the soffit and rises to a ridge vent or other ventilation device).

Ventilation is important for your attic and roof, so you'll want to be careful what you block up.

In my house, we used blow in insulation on the floor of the cap, and we used batting and foam board in the crawl space. You'll want to setup a ripping station outside, and you'll cut the foam board into lengths that fir through your crawlspace door. You carry them in in pieces, nail them to the rafters with special nails, and then use insulating/foil tape to seal the seams.