This is just an assumption as an example, if 5 million bitcoins can never be recovered again, then that would lower the maximum limit from 21 million to 16 million. So it is true as you said that the price of bitcoin will increase many times because the number of bitcoins is increasingly limited.
The price of Bitcoin will always increase because halving reduced the reward for miners and it reduced the supply of Bitcoin being introduced into the market. The lost Bitcoin also helps to make the Bitcoin will hodl to be valuable and this is why we have to keep holding the Bitcoin we own.
This is technically true. Well according to price history f bitcoin, for every halving marker the price of Bitcoin creates a new floor price and makes the price higher. Talking about the lost BTCs, it wasn't proven yet that it was truly lost. It just happened that there is about 5 million BTCs that are not flowing. Which means it is not being transferred or circulated in the market. If the lost wallets and BTCs are proven to be right, then I would take that as a bullish sentiment because it just really decreases the limited amount of BTC to 16mil.