My 3 Roses first year.

I am looking for some advice on the 3 rose bushes that I have. All 3 are planted directly in the ground .

The 3 are
Crocus Rose
Falstaff
Charlotte

They were planted about a year ago and bought from David Austin. All 3 are highly scented and each had several good blooms last year. I am now looking for help on bringing them on more this year.

I will be pruning them next month and know about pruning methods and cutting just above an outward facing eye. My questions are...

Each bush produced flowers but the flowers were really big and the stems were barely strong enough to take the weight. Is this something that will improve over time?

They were all planted at the same time about 2 feet apart but the middle one (Falstaff) does not look as healthy as the other 2 although I did see some new shoots coming along and am certain it is not dead. Would I be right?

When pruning, how far down should I prune to? I think I would normally go to about 10 inches from the ground, is that right?

What is the best food? Horse manure diluted or undiluted, some other food like you can buy from a garden centre or is there something else that everyone swears by and would that get rid of any blackspot?

How tall should I let them grow to?

Thanks

Nigel