> If there's no increase in stock price
Then the value of the company (and the expected dividend stream) presumably fell, in real terms, because inflation is typically nonnegative.
There's also depreciation. Most assets tend to decline in real value while simultaneously inflating. Companies may have a period over which the value appreciates, but the evidence points to eventual obsolescence. They'll probably liquidate their assets and give one final dividend at that time.
No. Selling is how investors get out. No need for a higher price because they presumably got a return via dividends. If there's no increase in stock price, there will be no capital gains on the sale price either.
Reinvesting all the profits into growing is a phenomenon that became popular due to tax law. A dividend paying company can still make the choice to reinvest profits rather than pay them out. That will just mean a lower dividend than if they paid out all the profit to shareholders.