A lot depends on what budget you have available or are prepared to spend?
Given your previous problems it sounds like you have had a series of badly fitting footwear which have not suited or fit your feet at all and in view if that I would suggest that you need the knowledge, advice and expertise of a professional bootfitter to ensure this is not repeated. Good bootfitters are are few and far between so you may need to travel a fair distance to find a good one and they don't come cheap.
If they are within a reasonable travelling distance I would highly recommend a visit to Whalley Warm & Dry
https://www.whalleyoutdoor.co.uk/boot-fitting-service/ who are an Altberg Premier Retailer and I cannot recommend their boot fitting service highly enough. Customers travel from all over the country to use their boot fitting skills and services and are highly recommended by many other forum members.
Depending on your budget the following models may be suitable options for you to look at.
2-3 Season BootsAltberg Fremington Men's 1412g RRP £184.99 (standard last with 5 width fittings)
https://www.altberg.co.uk/boots/5-width-fitting-boots/fremington-menAltberg Malham Men's 1344g RRP £189.99 (A-Forme last with 1 medium width fitting)
https://www.altberg.co.uk/boots/aforme-boots13/malhamAltberg Keld Unisex 1428g RRP £199.99 (G-Fit last with 1 wide width high volume fitting)
https://www.altberg.co.uk/boots/gfit-boots/keldAltberg's standard last is available in 5 width fittings from Extra Narrow to Extra Wide. If the model of a boot made on the standard last doesn't quite fit or suit your particular foot shape, width and volume it's a fairly safe be that a boot made on the A-Forme or G-Fit lasts will. All Altberg boots can be resoled if and when the need arises.
Expensive walking boots and lots of pavement/tarmac walking are not a good combination due to the high friction levels involved and sole wear. For pavement/tarmac walking training shoes or trail shoes would probably be a better option.
As a budget option for low level walking or daily dog walking I would recommend that you also look at the Altberg Defender military boots available via eBay. New from around £55 upwards or used from around £25 upwards and cheap enough to replace as and when they wear out. Unfortunately there's nowhere to try these on as they're not available to the general public so getting the right fit is a bit of a gamble and trial and error. If you make a sizing error just sell them on.
https://www.altberg.co.uk/boots/military-issue-boots10/mens-defender-combat-bootAny issues you are having with flat feet could be resolved by the purchase and use of appropriate after market insoles.
As already mentioned your first step is to start trying to soften and remove the hard skin on your feet & heels with daily washing combined with the use of a footcream. The process does take some time and you must persist with the daily routine to achieve results.