What tool do I need to remove this cassette? My FR-1 fits down in the splines correctly, but it won't budge.
Seems I need something to remove the smallest sprocket / lockring 1st?

What is pictured is a freewheel, not a cassette. The FR-1 is the correct tool. Unlike a cassette where the lockring is only as tight as the installation mechanic made it, a freewheel will get as tight as the greatest force from pedaling that has been applied since it's installation. Usually the torque multiplication of the gears and the greater strength of the legs means that a freewheel will be FAR tighter the any cassette lockring would be. A stout bench vice and proper body bracing while grasping the wheel/rim/tire at opposite points is needed. I've dealt with many freewheels that needed two strong mechanics to remove. Andy.

if you are saying that the FR-1 fits but the force applied is inadequate. use more force.

i use SS freewheels on many of my bikes, and i don't even mess around with them. the removal tool goes on, followed by a 10 inch adjustable wrench, and then a 2.5 foot piece of scrap drilling pipe over the wrench handle. they ALL come off. tire on ground, braced veritcally with shoulder and left hand, mild pressure on end of pipe and it's loose. resistance is futile.

as a matter of fact, when i see that old crusty freewheel in your pic i want, really want, to remove it.

As noted, this is a freewheel. They get as tight as the leverage of the large sprocket, the hills and the rider's legs make possible. Removing them requires the same kind of force.

IME, the easiest way is to place the wheel and remover in a vise, channel the spirit of Ralph Cramden, and take your bus through a hard left turn (without power steering).

If you don't have a vise, but do have a long wrench, fill the tire, and stand wheel between the wall and floor with the freewheel to the left. Arrange the wheel and wrench so you'll be pushing toward where the baseboard. Your weight on the wrench will jam the wheel tighter so it can't spin, and the freewheel will come off.

BTW- the wall/floor method is very effective, allowing you to put all your strength into the wrench, but arrange yourself so if/when the freewheel pops loose you don't tumble head first into the wall.

I don't have a vice or a long piece of pipe so I get my 12" crescent wrench secured onto the tool, get a good hold of the wheel, and whack the handle of the wrench with a heavy hammer. Not the ideal technique since the act of whacking the wrench usually causes it to disengage from the tool, but each whack moves the freewheel enough that after two or three, the thing frees up and off it comes.

Whatever method you use, I suggest you secure the FR-1 with the QR skewer.
Not tight, but "just there".
Once the FW starts to move, back off the skewer a little bit, else you'll have it bound tighter than a ..........

Try my brace the wheel in a corner and lean method. You'll be surprised at how effective it is, even without banging. Just don't bang your head when it lets go.

Dang!! That was tight.
Used FBinNY's 'lean / brace wheel against the wall' method. Worked! That, and a 2.5' piece of pipe for an extension.
A light smear of anti-seize will be applied during re-assembly.

Thanks for the tips, guys.

You going to re-use that freewheel?

Just be aware that all the removal methods suggested above, except the vise method, have the potential to bend the axle or the skewer, so check your work before and after reassembly.

There's no reason for a splined remover to bend anything if it's pressed fully in to the freewheel, and not allowed to slip out (either by skill, or by QR retention). The remover is well supported and kep on center by the freewheel itself.

Great analogy! "To the moon, Alice!"