c-lightning determine channel capacity
OK, the three figures you care about here are:

"msatoshi_total": 1600000,
"msatoshi_to_us": 1599884,
"their_channel_reserve_satoshis": 546,


They have 1600000 - 1599884 millisatoshis, ie 116.  But they need to keep at least 546 satoshis reserve, ie. 546,000.  Until they do, we won't let them spend any.

Hence the warning when you created an invoice: there's no way someone can pay it with the current channel configuration!