agree on the TDS meter not being a great indicator for system "health"
pressure should gradually fade away once the source is disconnected so no concern there.
3 months isn't a terrible length of time, but 3 approaches you could take...
Most expensive: replace all filters and media, clean all housings. The best peace of mind and no doubts about your water
Semi-expensive: replace sediment and carbon block, clean those housings. In theory, your RO permeate should be relatively clean so anything downstream of the membrane should be fine.
Least expensive: rinse everything out (minus the DI resin) and believe in your TDS readings
If you really want to nerd out...
Assessment of the extent of bacterial growth in reverse osmosis system for improving drinking water quality.
https://www.ncbi.nlm.nih.gov/pubmed/20512722
Great chart and the Scale at the bottom...
TYPICAL REJECTION CHARACTERISTICS OF R.O. MEMBRANES Elements and the Percent R.O. Membranes will remove
https://www.espwaterproducts.com/ro-contaminant-rejection-table/