There are a lot of people that seem to be having troubles with the difficulty. I think with any game if I ever have problems, I just lower the difficulty to easy and enjoy the ride. I just don't tend to have any patience.
Although tbh I didn't find Infinite all that hard. Even 1999 mode I didn't have too much trouble until the final battle and that was more because it is so chaotic and I brain farted on a key thing. I died here and there but it wasn't frequent.
I think a lot depends on play style and gear. The strategy I found which is fun and makes you mega powerful:
-Burning Halo (switch to Storm when not using charge a lot)
-Blood to Salt (switch to Winter Shield when in an area with skylines)
-Urgent Care (switch to Brittle skinned when needed)
-Overkill (switch to Vampire's Embrace when needed)
-Upgrade salts then shields
-Upgrade charge boost and charge aid asap
-Shotgun + Carbide
-Use undertow to take out entrenched enemies, sniper groups and knock tough enemies off ledges
You are now God
You have invulnerability+shield recharge once you hit an enemy with charge, tons of AOE and chain damage due to the charge upgrades, storm and/or overkill.
As for fighting the Handyman I really liked them just because they are so aggressive and keep ya moving. The strategy I found worked well if done right was to jump on the rails above them to get them frustrated. Then as soon as they jump on to shock you off, drop down and you can get a couple shots at their heart. You can also use undertow on them (or any other machinery) which not only short-circuits them, it also sets them right in front of you for a few seconds to get shots at the heart.
Here's a video with a similar set up.