For me, the bat must have an absolutely beast of a ping followed by the balance.
You are trying to replicate the ping of a "24 year old" bat which, by your accounts, aged extremely well and improved in performance over the years. Bad news: You are chasing the dragon.
1300 grams roughly translates to 2lb-14 ounces. That's an extremely heavy bat. Just the weight is enough to get distance for your shots if the balance is correct as in the original one you had. A reasonably well-pressed bat at that weight will get you there; question is do you want to persist with those specs or want to try something lighter, contemporary, and easy to acquire?
1. With the dead weight so high, I would probably need a low density wood. I saw on B3 website on how they have the best wood etc. hence one of the options. They also emphasize a lot on the wood being source from JR Wright. While I understand most of the bat makers source wood from JR Wright, some have other UK grown wood as well. Are the other UK grown wood inferior or less probable to perform that JR Wright's?
Are you trying to match weight of the original bat or volume? Does the original bat have thicker edges and spine compared to other bats of the era ? IIRC , heavy India made bats did not really have disproportionately large volume, the batmakers used high-density willow to make heavy but normal sized bats.
2. Can a bat really be replicated entirely with the similar balance?
If the bat maker holds and sees the original bat, probably yes if you are lucky. A bat resulting from written/verbal specs will not satisfy your senses. General answer to your question: No.
3. What kind of handle is used at these manufacturers? I read a lot about 12 piece, carbon infused etc. Does it make a huge difference? Gray-Nicolls definitely thinks that.
Laver & Wood have a handle that puts a carbon honey comb in the top tip of the handle to manage handle flex. You are going down a rabbit hole. You are better off playing the "how it feels in my hands" game rather than technical minutiae.
Save yourself lot of headache, heartache, and money by testing modern bats instead of replicating an old dream. Newbury has some great options. Millichamp and Hall used to have a bat called Amplus and in heavy weights too - it hit like a dream. I'd stay away from Gray-Nicolls. If you can find a reputable dealer/shop, CA is a great options. If you can find an older CA, you'll save tons of money too.
You can search my old posts for other information but my favorite bat shapes are Newbury Blitz (designed by Tim Keeley) which I had replicated (custom made) by Keeley as well. You can hit easy sixes with a CA.