how did you produce the curves? traced them of some drawings? maybe it would be easier to redraw them again in future knowing that you should end up with smooth curves so using less points may be better. also for hard edges you can draw piece by piece and join it after that. that will also be the method of rebuilding them now. and i will also very slightly change (smoothen) the geometry along the procedure. so if you are not ok with that and really need your bumpy curves then we have to rethink it.
i can see you resulted the upper curve through a simple 2d scale and moved it along the z axis. that might work later on, but first we have to clean up the initial curve. if there is no other way and redrawing is no option, we can first trim the lower curve. you can mirror and join them later. that is just that we dont have do do the same work twice.
i also saw that you have some interruptions those all have to be rejoined and delete the conjunction point.
anyway first explode the remaining half rejoin the parts which should remain one continuous curve and use
between the hard edges you can select the round leafy parts and use
Fair a couple of times just keep hitting the space bar till it has an acceptable continuity
after that you can use
FitCrv. for the best results through the entire build up i used the following settings
you can still play with it but it resulted in few but accurate points. i also lowered the degree to 2.
on this one below there is plenty to do
this will smooth out using Fair again a couple of times till its good enough for you.
here again in particular you have to rejoin those and delete the connection edit point it will result in one continuos curve do that with all interruptions. after that use Fair and FitCrv. also use fair and fit curve on the straighter parts between the hard edges.
do that till you have all parts reworked and rejoin the whole side mirror it join scale and move along z as you did before. then offset each curve the upper and the lower. the inner ones can be done with loft the outer ones i had to use sweep 2 to get something acceptable. then you can use cap to cap the outer surface select the inner and trim the middle part of and join all together to one solid volume.
here you go the finished file so far it could be done maybe a bit better but its usable for sure.
Block letteringhelp new.3dm (3.1 MB)