Turkey, I think there's a some things you should think about here. First, no matter how you lube the bullet if it doesn't fit the bore you will get leading. But you say you're already at 1900 to 1950 fps so I think you've already covered this angle.
Second, assume that you're shooting 1 & 1/2 inch groups. By speeding up the bullet to 2300 fps and you start getting 2 to 2 1/2 inch groups - does it really matter on a deer sized target? Better to give up some accuracy and gain terminal performance if that's the way it works out.
Third, if you make the bullets too hard with a round nose bullet you'll end up with a pencil sized hole through a deer that will go a long ways before it goes down. Better to keep the alloy soft and hope for some expansion.
Fourth, if you want a hard bullet going fast that will perform on deer, consider a flat nose bullet. Lee, Lyman, RCBS and Saeco all make flat nose bullets that depend on the flat meplat to make the hole and provide provide the terminal performance you're looking for.
With that said, I took one deer with a 35 Remington and Lyman's 358315 (205 grains, round nose, gas check) with an alloy of 1/2 WW's and 1/2 Linotype running full loads at around 2000 fps. Worst performance on a deer that I've ever seen. Was just pencil sized holes straight through the deer and it took a long time to go down.
Since then I've used Lyman's 358627 (220 grains, SWC, gas check) at about 1600 - 1650 fps, and RCBS 35-200-FN (210 grains, Flat nose, gas check) at about 1700 fps in a 35 Whelen. Both were with air cooled WW's. I couldn't ask for better performance. The SWC is very deadly, but the FN does very well also. The SWC's typically have a 1 to 1 1/2 inch hole clear through the deer, the FN's usually have a 1 inch hole right through the deer.
I've also used a custom mountain molds 9.3 (.366) mould and gotten excellent perfomance out of a 9.3x57. This is a 300 grain bullet, flat meplat of .270, gas checked. The deer just drop with a hole 1 to 1 1/2 inch clear through. This was with air cooled WW's also. Speed right around 1700 fps or so.
Bottom line, to take deer with a round nose cast bullet the alloy should be soft to hope for some expansion. Expect to give up some accuracy and perhaps get a some leading. The leading won't matter much with the few shots you'll take during deer season. Or, get a flat nose mould where you can get make the alloy harder, keep your accuracy and get human kills.