"buying a chain wear indicator when a ruler is more accurate and cheaper" Simply wrong. Sheldon's ruler trick way too vague.. if your running something above the 'junk class'.
"Any 5-6 speed freewheel of the ratios you need is probably fine". Begs the Q: which one is the OP riding now and are they satisfied with that gearing? 5's suck... the jump between 14-17 is too wide.. unless your dawdling along always.