Is there a way to pre-generate 1000 subaddresses from your monero private key?
Generating subaddresses from a private view key explained in this answer and on the monerodocs site here.
And then say I sent some xmr to the 979th subaddress, would the wallet see it or do I need to do something first?
The default wallet lookahead indices are set to 50:200 (...
Each Monero transaction contains multiple inputs/outputs. It is not expected that you own all of the outputs of the transaction; only those destined for you.
The utility you used is reporting:
This address owns output 1 with pubkey: 238a...48ce for amount: 0.297602
Which indicates that your address did, in fact, receive 0.297602 XMR.