You say this is a reputable rescue, yet also say they think it acceptable for a dog to be left 7hrs! That goes against all good, well respected dog welfare groups, suchas RSPCA, PDSA, Dogs Trust, etc, who all say a maximum of 4hrs. I would run a mile from a rescue who thinks 7hrs is fine.
Whilst a LL is highly unlikely to go to the expense of evicting you for your dishonesty and contract breach, with regards to the guinea pigs- they will now view you in poor light. Which is so silly, when if you'd have been honest and up front they in all likelihood wouldn't have minded guinea pigs and you wouldn't have given them a negative view of you from the start.
Also it doesn't matter how many years you've rented or paid rent on time, the fact of the matter is you paid this landlord late whilst a new tenant. Which again puts a very negative view of you in place.
Creating two such negative views of you right from the start of the tenancy (dishonest / ignorant of contract and financially unreliable), will not help get a landlord to trust you not to let a dog destroy the place.
Also I would be very surprised if your guinea-pigs really are in no way what-so-ever, worried by being housed indoors with a predator. It would be unusual, they normally need a long adjustment period, dog kept mostly in other rooms and a dog that is small fury friendly - as in ignores them 100%. Is this rescue dog even small furry tested? Will guinea pigs cage be able to be in a room the dog is locked out of, when you are out? Dogs can, and some will, break into small furry cages, whilst owner is out.
If the property is basically a shit hole, as your drip feed says, then you would be somewhat more likely to get a dog agreed, although I really do think you have damaged your chances with the silly dishonesty and contract breach, plus the financial unreliability you have shown this landlord.
I'm also wondering if you are expecting to be in a family owned rental and thus allowed a dog in the next 6-12 months, why on earth you don't just wait? It's not that long in the grand scheme of things.
Also I think it rather sad how you felt so insulted you had to make a ridiculous insult back in suggesting that no-one who has taken the time to answer you could possibly have rented/ know anything about renting, when most of us have actually stated we are in private rented or a landlord! As I said in my other post, I myself have pets in my private rented accommodation.