Welcome to TBN.
The hydraulic fluid flow is very minimal on tractor especially for a backhoe so I don't think there is much you can do about it. A backhoe on a tractor is pretty much a single operation at a time (lift, extend) unlike a true dedicated backhoe or a excavator in which you can curl, lift and extend all at once because of the increased fluid flow capacity.
Not sure what NH you have but at the time when I purchased (20+ years ago) my backhoe for my TC33D there were not the options that there are today. If I was looking for a backhoe today I'd be seriously considering a mini excavator. There are a number of them for about the same price as a subframe mounted backhoe that can to do twice the work of a backhoe mounted on a 30hp tractor.
