Its not the amount that matters so much as the contaminants it contains. REcrystallizing isn't done so much to make diamonds as it is to clean trace elements of nasty substances out of the meth. To make it food grade. Consumable.
The diamonds... are just gravy, so to speak.
You may have a problem with not getting the pseudo clean enough. It sounds to me like you have a crystallization inhibitor in the mix still. Polysorbate 80, perhaps. Maybe one of the Eudragit polymers.
IF you have polysorbate 80 in abundance, your efforts will result in a substantial loss of yield. You may elect to do the dirtier meth and have it to do. I've seen it take four passes to get the polysorbate 80 out of the mix post reaction, and the loss of yield was substantial. The Eudragit polymers have a similar effect. These, however will rextal on the second or third pass, but may not form crystals after that. Your problem is not your choice of alcohol, or the absence of water. Your problem is most likely in your pseudo extraction... you aren't getting it clean enough to begin with.
You can also do the rextal process with the pseudo. Just remember that any loss of yield at the pseudo stage is probably the loss in weight of something you didn't really want to react anyway. If you can't get the pseudo to rextal, you can bet you don't have it clean enough to react. You will get some meth, yes. But yields will be low and the product will be contaminated with the stuff you have now.
With good clean pseudo, lacking the polymers, polymer fragments, or polysorbate 80 or PEG, you can recrystallize amounts as small as half a gram with little loss. IF you don't know, a gram to a gram and a half is probably a cut off point. Below that and your fixed losses are high enough that if you have a problem with growing crystals, the losses are so high you won't have enough left to be worth doing the work it took to clean it.
