Er... I'm not so sure this treaty is realistic. At all.
Japan in the 1890s is not Japan in the 1900s, and I'm not sure they would've been able to sustain a war effort of that kind with Russia that early without some serious losses. Russia is not fighting a huge landwar with Germany to suck up huge resources, and a war in Central Asia favors the defender, largely. While any Russian advance into Afghanistan might be disastrous, a British advance into Central Asia would be too. Especially since the Afghans were historically anti-both, British protectorate be damned...
There's a nuanced relationship between the British and the Afghans and it was one they carefully balanced. Afghanistan would be totally wary of British soldiers staying on once the Russian threat was removed.
Who are the British backing as king of an artificially created Turkistan? There certainly wasn't massive support at this time for one.
Why was Indochina conquered so quickly? The Royal Navy may be powerful, but the Marine Nationale isn't crap, and Indochina would've been a long campaign; Japan trying to invade would definitely have been a horrible setback for the Japanese themselves. In addition, the British wouldn't have annexed it, as they were wary of adding another India to their Empire- Indochina would need a massive influx of British administrators, even for simply the directly administered areas.
France would not surrender Senegal or Gabon or literally any of those territories south of that line you've drawn up. The French Empire is a point of pride, and you've essentially left them with a lot of desert. And again, now Britain is left to administer a bunch of land they don't really need or want.
Also, Fabian plans or not, trying to redraw African borders into tribal ones would be massively expensive, and arguably not worth it. In fact, I'm sure trying to convince Parliament this is the best idea will totally not be worth it, especially since those straight line borders prevent any real tribal borders anyway.
You've also completely underplayed the racial tensions that would've occurred within the British Army. Indian soldiers would have been the majority of soldiers fighting in Central Asia, and many would be apprehensive about going through Afghanistan. By relying so much on Indian soldiers, you've also created a political problem for Britain in the future, but that's one to deal with later. It would also still be an ineffective army, divided into three parts, with only the Bengal Army initially being present in the Northwest. Britain would've needed to gain political support in India for more and more soldiers to go beyond the northwest. Indian soldiers would not be happy about going beyond Afghanistan at all.
Japan would not get Primorye and Russia's warmwater Pacific port, and they wouldn't have the capabilities to take it. Japan would overextend itself trying to invade that deep into Russia. Manchuria is one thing, Russia another. The soldiers there would be enough to send the Japanese packing. Vladivostok would remain under Russian rule, even if the Japanese rule the seas there.