Byant, the 60-61 is just right for a small knife (say under 8” blade length) of 1080, with no extra carbon to help out in abrasion, going softer will not give the edge holding you may want. The problem is in giving an exact temp to go to. I have been tempering knives for over 25 years and still do not have a set temp for every knife, but sort of get the feel and adjust each one accordingly. How they made the steel, what you did before the heat treatment, the temp and time you were at before quenching and the effects of the quench will all have a profound influence on what temp you will need to put the steel right at 60-61 HRC. If you are confident that you got it fully hard after a decent time at temp, then you can start out at 400F in a kitchen oven. If temps at 375F or below allows you to put the knife to any sort of hard use, you may not have nailed the heat treatment as well as it could have been. At any rate tempering is good for steel, so start at 400F and then try out the blade, or get some Rockwell numbers off it. If you feel you need a little less hardness then bump the oven up to 420F-425F and run it again. While it is not at all precise or definitive, as a broad rule you can assume 20F more in temp will get around 1 point less in Rockwell.
On the handle shaping, most guys when starting out assemble and then finish, it is a quick and easy way to give a very clean surface and finish, but as with all things that are quick or easy it is also rather simplistic to deal with the more complex concerns of higher end premium custom knives. One of the foremost issues would be the fact that natural materials will move and your knife will only have that nice clean and flush look or feel for a short time after the assemble and finish operation.
In your position, right now I would cut things as close to the metal as possible and then assemble for finishing. Later on as your finishing skills increase you will see increasing need to precision fit before final assembly, and explore many methods to treat edges with radii, chamfers or decoration. A guy paying $100-$200 for a knife will live with some later gaps or ridges, the guy spending $1,000-$2,000 will probably send it back to be fixed, so the maker of that range would probably be wise to nip the problem in the bud before sending the knife to begin with. The latter customer will also probably be looking for those attentions to detail before he opens his wallet anyway.
