Yes, the tube should be removable, it has the same standard threads as any AR-15 buffer tube.
Yes, this brace will fit that firearm.
Yes, it should, per SB Tactical, "Adapter machined to accept flat and sloped AK receivers".
This is the AK adapter with a pistol spec buffer tube, which is a straight tube. It has no holes or adjustments and accepts standard pistol braces with a diameter of approximately 1.10-1.25".
From what I am aware of this is a straight tube. You would have much better luck getting the adapter alone here:
https://www.opticsplanet.com/sb-tactical-brace-adapter.html
And then getting whatever buffer tube and attachments you want.
No, this is a pistol buffer tube. The SBA3 comes with a MIL-SPEC buffer tube. You will need just the adapter which can be found here:
https://www.opticsplanet.com/sb-tactical-brace-adapter.html
No, it will not. This is a pistol buffer tube and the SBA3 uses a mil-spec buffer tube. You will want this:
https://www.opticsplanet.com/sb-tactical-brace-adapter.html
That is ONLY the adapter and does not come with the tube so you can use the MIL-SPEC buffer tube that is included with the SBA3.
No, it will not. This is a pistol buffer tube and the SBA3 uses a mil-spec buffer tube. You will want this:
https://www.opticsplanet.com/sb-tactical-brace-adapter.html
That is ONLY the adapter and does not come with the tube so you can use the MIL-SPEC buffer tube that is included with the SBA3.
This adapter will come with all of the hardware required to install to a standard AK receiver and grip.
This adapter will accommodate any pistol brace that mounts to a standard pistol buffer tube with a diameter of approximately 1.20 inch diameter.