We all love the Savage for what it does well - but as you have noted the highway speeds over 60mph for extended periods is not what it does best.  For me the Savage is a great bike for rides on rural roads, mountain curves and a running out to do errands...it is not a touring bike made to do long rides on the highway.   You can actually make it better by hopping up the engine, changing gearing, installing an SV650 front caliper or Shawn's big brake kit, etc.  In doing so you will end up with a better performing bike - and yet it is still going to be a Savage at the core.

You have mentioned a few bikes that are very nice:
MOTO GUZZI:  I have ridden both of the Moto Guzzi's that MM has owned, and I have several friends that own them.  Their personality is very much like the Savage - nice low end torque, smooth engine and capable handling.  The fuel tank is almost 2 gallons more than the Savage, it has a lot more HP and is very capable of cruising at highway speeds, it is shaft drive and maintenance is pretty easy.  Parts are definitely easy to get and there are lots of aftermarket items available - dealers are not always close to you.

Triumph:  I have a friend with a 1200 Bonneville.  It is a much bigger/heavier bike than the Savage - but boy does it have torque and HP!  My friend has had very little trouble with his bike - it got a cam chain rattle about 6 months after he bought it and it was a factory warranty issue (Triumph has since fixed the issue that caused it).  Bill shipped the bike to the UK and rode it double with his wife for 6 weeks and they had no trouble.  The bike is very smooth and comfortable and it handles great - a 1,200 cc bike is a very capable touring bike.

Royal Enfield:  The only RE I have ridden is MM's 350.  It is very comfortable and smooth, the bike looks well made - however the approach at building some components looks a bit sketchy when compared to what Honda/Suzuki/Yamaha would have done.  The shift lever is made from steel plate - however MM has never reported that it doesn't work well and it shifted just fine when I rode it. (Photo of 350 shift lever attached - it is made from steel sheet rather than cast).  MM loves his 350 for local rides - but the 21 HP is only 2/3rd what your Savage has and it is not really a touring bike either.  MM has added parts to bump up the HP a bit to try and make it more suitable.  MM also has a RE650 when he needs the extra power - but he hasn't said much about it????????  I rode with Armen in NC/TN for a couple of days and his friend had a RE 650, and he loved it.  They are several models of the 650 and they are great looking bikes.

Kawasaki W800:  This is a nice looking motorcycle and it should be very reliable - it is an upgrade from the W650 they made 1999-2007.  An 800cc twin will have plenty of power and torque to do anything you want to do.

Honda NC700.  There are several variants of this bike - some have forward peg position and some have mid pegs.  The fuel tank is under the seat which provides room for a "frunk" where the fuel tank is normally located - and I believe it is big enough to store a helmet!  Stewmills has one and I have ridden it.  The bike is smooth and rides pretty nice - however I had just climbed off a bigger bike and it felt a bit more sensitive to small pavement bumps than the one I had just been riding (maybe not a fair comparison in retrospect). It is not classic styling - but it is a motorcycle that will be reliable and keep you riding for years and years.

BMW:  You may not be able to find a bike with Classic Styling - however my F800GT is the best bike I have ever owned/ridden.  The size fits me very well, it rides double easily, it is smooth and fast, it cruises at highway speeds easily, it gets good fuel mileage, and it has a maintenance free belt drive!  The seating position is much better if you get some handlebar risers, the stock windshield was a bit short for me and put the wind right at my throat and made my helmet noisy, it puts a bit too much engine heat on your legs when the ambient temperature is 90 and above.  I currently have 37,000 trouble free miles on my bike.  The engine is built in Austria by Rotax - it has a noticeable amount of valve train noise - but 100,000 miles or more is not uncommon from owners who ride a lot.  There is an earlier ST version with a bit less bodywork, and F800R that is chain drive and more of a naked bike, and the F800GS with a chain drive and Adventure Touring bodywork that are very popular - as they are much lighter than the larger R1200GS and still have plenty of power to go anywhere you want to go.

Suzuki:  The SV650 and SV1000 are not very pretty bikes - but they are rock solid and have a large following of devoted riders.  Aftermarket parts are plentiful, and they are capable of doing anything you want to do.  There is likely a large supply of used bikes and it should be easy to find a well cared for and low mileage bike.

VulanS:  The Kawasaki VulcanS is a 650 parallel twin with a cruiser layout similar to the Savage.  The 650 parallel twin will easily do highway speeds.  It is not a classic "standard" look - but is a pretty bike.      

CRUISERS:  If you are OK with a cruiser layout, used Honda Shadows and Suzuki Boulevards are plentiful and affordable.  I am not a fan of the sound/feel of V-Twins - they just aren't built with a lot of power for the engine size and they sound like they are working too hard at highway speeds.....but some folks cover a lot of miles on them.  There are lots of older fellows who bought a Cruiser thinking they were going to become bikes - then fell out of love with the idea......there are a ton of them for sale at good prices.

Either this month's or last month's edition of the AMA magazine had a review of https://www.motomoriniusa.com/calibro-bagger. It's a 693cc parallel twin with EFI. Moto Morini is a older Italian name plate that they're bringing back using engines from https://www.cfmotousa.com/about-cfmoto who used to make them for Kawasaki. In fact, this egine was the one that was used in the Vulcan S.