Dogs connected to bikes are not a great combination for a bunch of reasons.

If you want a more efficient higher torque bike you will want to actually spend money on the bike. Yes there are certainly vehicles that cost the same as a basic low initial cost hybrid and also manage to have electric bits and bobs but the quality and support just cannot be there and if you want certain specs you are unlikely to get there, they are designed just to hit a price point and that means compromises everywhere.

I would look at something with a Bosch Performance line motor which is going to be 85nm of torque or look at one of the Brose S motors which is 90nm and both are good reliable well supported motors/e-bike systems. They are also mid-drives so you eliminate the inefficiencies of the hub drive and you can have a stronger rear wheel which is going to help with the extra weight. These might not be in those lower initial price points but long term will be a better option.

Good luck with the weight loss and good luck finding bikes. Your local shop is likely to be a good place to start especially if they know e-bikes!