2) The data sheet hints (page 246): "The SMBus interface is stalled while SI is set; thus SCL is held low, and the bus is stalled until software clears SI.". Perhaps I can manually set the SI bit in SMB0CN and with a separate "RESET" flag indicate that the ISR shall not clear the SI. Wait for 35 ms, clear the "RESET" flag and the SI bit. Any pitfalls in this logic? 

doable BUT you do not want to hang in an ISR for that long..

an idea for you to think through

in main disable the the SL interrupt, set SL set a flag start a timer, in the timer interrupt disable the timer clear the flag and enable the SL interrupt

yes a typo and since edit did not work I posted a correction

Can you provide some reference documents for design schematic?

I could spend some time digging, but why? just add the pullup

just reakized theat a devboard schematic might do

just refer to the fact that RST is pulled up, no need to copy the rest

https://www.silabs.com/documents/public/user-guides/C8051F560DK.pdf

yes a typo and since edit did not work I posted a correction

Can you provide some reference documents for design schematic?

I could spend some time digging, but why? just add the pullup

yes a typo and since edit did not work I posted a correction

Can you provide some reference documents for design schematic?

I could dig, but why? just add the pullup

yes a typo and since edit did not work I posted a correction

Can you provide some reference documents for design schematic?

I could dig, but why? just add the pullup

re programming pins

by sheer necessity they must work after reset, so I would just leave them alone in the default state

are you doing pin sharing?

is this  your only board, or can you try programming another?

I fear that 'playing with' the programming pins you may have set one to push-pull and burned something in the programmer

re programming pins

by sheer necessity they must work after reset, so I would just leave them alone in the default state

are you doing pin sharing?

this makes no sense, so a couple of guesses

I once found a 1M resistor soldered in place of a 1k

is the 1k pullup actually connected