kept him shod in the front because he has soft feet
You need to do your homework, learn the pros & cons of shoes & other approaches & make your own *informed* decision, as you will hear different opinions on this, many based on little or anecdotal information. There are also fanatics on either 'side of the fence' and you need to read/listen with an analytic, objective view & take everything with a large rock of salt
. Unfortunately there's no shortcut to doing your own study & weighing up pros & cons, if you want to truly make the best decisions for your horse's sake.
I think Mayfield Barehoof Care Centre Home Page Equine Lameness Prevention Organization
are 3 good sites for more info, to get you started.
That said, agree with others, & to a certain degree your farrier, that IMO it would be a good move to get the shoes off, to start with at least, & at least for regular periods throughout the year, because being shod long term without respite is not great, even if shoes are 'needed'. I also believe conventional shoes are *generally* contraindicative of unhealthy feet, so if your horse has hoof issues, I'd tend to want him unshod until his feet can become healthy & strong.
BUT if he has 'soft' feet, if this means thin, soft soles/frogs, he may well need protection/support, for work at least(unless horses have very serious issues they don't need protection in the paddock). So while I'm all for *shoeless*, that's not to say I think *bare* is necessarily always best. IMO boots, pads, casting, etc is generally a better option than conventional steel rims, which can indeed make the horse more comfortable & reduce feeling, but can do further damage by peripherally loading the hooves & providing no protection/support under the foot where it's needed.
In the pasture this has not been a problem as his feet get sand/mud in them before they get snow in them. But when I clean his feet to ride, he gets ice balls.
Don't clean his feet before a ride then
But I am concerned. I read that horse's feet can be very sore after having their shoes removed.
If your horse's feet aren't too bad, they shouldn't be sore just from having shoes removed, but like yourself if used to wearing shoes & lacking calluses, they may be a bit sensitive on hard/rough surfaces.
Severely compromised feet can indeed be sore immediately after the shoes are removed, because suddenly there is more feeling in them. Also if a horse has thin flat soles from having them suspended off the ground, removing that 1/4" of 'buffer' puts their feet(eg. pedal bone with little 'armour plating' under it) directly on the ground. IMO this is far from a good reason to just whack shoes back on, but they may well need protection under those soles, or to be kept on yielding footing for a time, while their feet become healthier.
How sore will he be and for how long if his shoes are removed?
Can't answer that, not having much at all to go on. There are so many factors that even with hoof in hand, 'it depends' is the only straight answer. Your farrier sounds like he may have some good knowledge to share though.
If you would like some specific opinions/advice on your horse's feet, there are a fair few hoof-knowledgeable people on this site & posting pics(see link in my signature below) & more info on diet, management, etc would be helpful.