Hi Nester,
Because Valium has a considerably longer half-life compared to Clonazepam, when you cut part of your Clonazepam dose, you blood levels of Clonazepam will leave your system much more quickly than it will take the Valium to build up to replace it. There is disagreement about what would constitute an equivalent dose, but there is huge variability between individuals anyway, so 'an equivalent dose' can be only an average at best.
Because Valium takes some time to build up campared to the Clonazepam leaving your system, and since you have already tried substituting part of your Clonazepam dose and failed because of withdrawal effects, ask your doctor if you could take a 'loading dose' the first time you substitute part of your Clonazepam dose. So, instead of substituting 0.25mg Clonazepam for 2mg Valium (as your first doctor suggested), you would take 4mg Valium for the 0.25mg Clonazepam instead, but just the first time you take it. This will shortcut the time it takes for the Valium to build up in your system. After this first 'loading' dose, you would then take 2mg Valium as replacement for the 0.25mg Clonazepam you have substituted. Of course, 2mg might not be a high enough equivalent for 0.25mg Clonazepam, and time will tell. You should discuss this possibility with your doctor.
After you have adjusted to this first substitution, and you are ready to substitute another part of your Clonazepam dose, you would again take a double dose of Valium for the new reduction of 0.25mg Clonazepam, and take 2mg Valium for subsequent doses, just as you did with your first substitution. You would do this with each new substitution. I would allow at least a week between each new substitution, but allow longer if necessary.
And to answer your question: if you find it too tough to cross over to Valium, then yes, taper off Clonazepam instead. When at lower doses, if you need to make smaller cuts than is possible via pill-splitting, you can titrate your pills (make a liquid) to manage smaller cuts. There are advantages and disadvantages to switching to Valium, you just need to decide what's best for you.