Then analyses of a text #3

The narrator recalls his adolescence.
He is an apprentice for the lawyer Mr. Spenlow.
His grand aunt and her best friend came to London after her going bankrupt.
He encountered his best friend Agnes, who came to London to meet his grand aunt, came to his apartment with her.
After a while, Agnes' father, a local lawyer, Mr. Wickfield and his partner, Uriah Heap who had been his clerck, came to.

'I am well aware, Master Copperfield, that Miss Trotwood, though an excellent lady, has a quick temper (indeed I think I had the pleasure of knowing her, when I was a numble clerk, before you did, Master Copperfield), and it's only natural, I am sure, that it should be made quicker by present circumstances. The wonder is, that it isn't much worse! I only called to say that if there was anything we could do, in present circumstances, mother or self, or Wickfield and Heep, -we should be really glad. I may go so far?' said Uriah, with a sickly smile at his partner.
'Uriah Heep,' said Mr. Wickfield, in a monotonous forced way, 'is active in the business, Trotwood. What he says, I quite concur in. You know I had an old interest in you. Apart from that, what Uriah says I quite concur in!'
'Oh, what a reward it is,' said Uriah, drawing up one leg, at the risk of bringing down upon himself another visitation from my aunt, 'to be so trusted in! But I hope I am able to do something to relieve him from the fatigues of business, Master Copperfield!'
'Uriah Heep is a great relief to me,' said Mr. Wickfield, in the same dull voice. 'It's a load off my mind, Trotwood, to have such a partner.'
[David Copperfield by Charles Dickens]
1. I'd like to know what "called to say" means.
2. I'd like to know what "I may go so far?" means.
3. And I'd like to know how "to have such a partner" be in an apposition to "a load off my mind."
Thank you in advance for your help.