Bravo for your efforts. Previously I had Silverudd Blues and loved the breed. They are well worth the effort you will put into them IMO.
It seems that the ORIGINALS were somewhat different from the ones that GFF subsequently got. The originals (and some of mine were frome Omega Hills, some from a person who got theirs from the First GFF imports)--- The originals had very dark, almost black-lloking eyes that were very luminous. The next ones that GFF farms was selling had yellow eyes.
I always bred Isbar to Isbar with the exception of some Isbar to Cream Legbar crosses, and we called those Ice Cream Bars. There was hybrid vigor they were also great birds.
People who got GFF birds that were probably fairly inbred from the beginning paird brothers and sisters I think, and never made the effort to seek out different genetics. The result was a disaster, the chicks either failed to hatch, hatched very weakly and subsequently died or didn't all grow to adulthood and people abandoned the breed rather than work with it. They were some of my all-time favorite chickens both for beauty and for temperament and the hens were producing huge green eggs with great frequency and the hens were not big food guzzlers. They really 'earned their keep'.
Temperament was outstanding - had one rooster -- hatched in 2014 at Omega Hills and sent to me (July 2014), that did develop respiratory problem his first winter (2014-15). I brought him into a house I had just moved into and he lived in the entry hall rather than outdoors for a long time. Some nights I would be upstairs working on the computer and hear him gurgling and wheezing and think 'he will be dead by morning'. However he lived -- and just died this summer. Perhaps due to time indoors, or being ill and nursed back to health he was amazingly friendly and talkative. He was the very best rooster I've ever had.
A local friend had more Isbars than I had and we worked to source the ones we considered correct (Very dark brown eyes - and confirmation (I should say 'type') of a pretty chicken). Between us, I think that we did improve the hatch rate and health of the chickens we had. My focus was Cream Legbars and not Isbars.
So my long term point is that this breed is well worth work that you would put into it. I'm downsizing chicken activity and have even sold my pens.
If you get responses -- or even directly PM some of the Isbar owners from the threads (I think there are a couple of threads on either Silverudds blue or Isbar or Blue Isbars -) You may find a network of people working to preserve these genetics. Even Omega Hills if they haven't minded to a large extent diversifying the ones that they have, may be slipping into close breeding -- which is OK sometimes to preserve and promote traits and others can weaken the genetics as GFF claimed they had suspected with their first Isbars, as you say.
For out cross, I'm curious why you selected RIR -- it would add their brown genetics to the egg and deepen the green (as our Ice Cream Bars perhaps reinforced the blue side of the Isbar's green eggs).
At anyrate, if you are able to breed these, and select your hatching, surviving and healthy individuals to pair with quality Isbars (I would seek a private breeder from BYC here if you can locate one that really cares specifically about this breed for either hatching eggs or chicks) -- perhaps you can help preserve the 'true' Isbar. It really would be a worthy effort.
I'm far from an expert, but if I can share any of the experiences I had with this breed and it would be of any help to you -- feel free to PM me.
There is also a product called Denegard that is widely used in the UK and has no egg withdrawal etc. that a vet from Texas A&M told me is the very best treatment for respiratory problems in fowl -- wish I had known about it in the winter of 2014-15 because it probably would have eradicated the respiratory problem of my rooster in a matter of days.
Good luck with your Isbars!
ETA Whoops, just re-read most of this thread and looked at the picts. I should be saying Silverudd's Blue--- and NOW I see why you chose RIR as the outcross.
I enjoyed your post and wonder if you happen to have any photos of your icecreambars or their eggs? There’s limited photos online and I am hoping to do this cross in the spring but not sure what they’ll end up looking like....
Glad to see that this thread is still active. 
