Vintage bike, new chain
The derailleur in the second picture does not look over extended. If the derailleur has some movement left in that position then it's OK. If it's up against the limits and is being bent then you will need to lengthen the chain.

Just for future reference, you should size a chain using a proper procedure: Thread the chain around largest sprocket and chainring (not through the derailleur), find shortest chain length with where inner and outer links, add one inner and outer link.