https://industrypro.co.th/en/product/water-pump-constant-pressure-mitsubishi-ep-series/
Your pump switch setting is 2.8 to 2.4 which makes it 200 or 250 see below. With a max discharge of 2.8 bar. EP-200 or 250 has a potential max discharge of 4 bar.
https://industrypro.co.th/en/product/automatic-pump-mtsubishi-wp-series/
OP's pump is a WP type. 200 0r 250 watt. Changing it to a Mitsubishi EP type of the same wattage potentially would give about 15 - 18 psi more. Or 1 to 1.2 Bar if you prefer.
Not a direct replacement so would need some modification to the existing piping.
If he lives untill 85 that is a lot of years.
I'd say 9 million
Put 5 million in some sort of fund and draw down the remaining 4 million for 5 years then withdraw 4 million from the fund and start again.
We need to account for inflation, present-day value, etc.. so someone with more financial savvy can work out the exact numbers.
I run LPG which is hard on plugs and ignition system. Used to be difficult to find heat range 6 plugs instead of stock 5 as dealers only sold std. plugs for specific vehicles. So I changed the 5 at every oil change. Now I can buy cheap "taxi" plugs but the habit persists.
https://www.ngk.com.au/technical_info/lpg-compatibility/
Unlike other countries, the labour cost for changing plugs is not that great so you don't need super long-life plugs. I replace mine at every oil change. So, for me, every 10,000 kms.
The set I bought for my truck were 250 Baht. 2000 each sounds a bit steep. Unless the Civic engine needs to be removed to change them. Most expensive on lazada 1350 a set.
The one I bought for my scooter was 388 but..the only 10 heat range I could find.
Rock is the same as a Honda Dream. If the dealer is close OK. I wouldn't trade dealer distance for cheaper price.
Above is the same as Super Cub.
If just for around town? Splash out a bit more?
More storage