You don't have a multiport valve, you have a push/pull backwash valve. It doesn't have a recirculate option.
If you want to take control of your pool and save money in the process, order a TF-100 and a Speedstir from TFTestkits. Test results from pool stores can't be trusted. Also, get the
PoolMath app and learn to use it. Source liquid chlorine locally - Lowe's, HD, Ace, Walmart and a few local pool stores carry it. Read up in PoolSchool and adhere to the
FC/CYA Levels.
If your water is 7 years old, the CH level is probably much higher than what the pool store results indicate. CH can only be reduced with water exchange - drain/refill and splashout. CH continues to increase with water evaporation. And your fill water - if not using a water softener to furnish refill water - is between 200-250. Since we live in the desert and pretty much the entire pool volume evaporates every year (or more often), your CH increases at least 200 per year.
If all you have been using is 3" tabs, chances are your CYA is much higher than listed also.
If the filter pressure increases rapidly - you have an algae issue. Chances are you equipment is fine.
Best bet may be a drain/refill. Just be aware of our increasing temperatures (90+ for the next week or so) and if you do drain, use a hose to keep the pool surface damp. Uses as many hoses as possible to refill. Your other option is to wait for cooler weather - but it may be a while.....