The fact that Clutterbuck is on the roster is also the reason a guy like Hudson Fasching makes the team. Had Lou not re-signed Cal (on the day he was having back surgery!), there wouldn't have been this constant need to dedicate a roster spot for a replacement for the 40-odd games Clutterbuck usually misses.The estimated amount on Capfriendly is correct. The Islanders will have just shy of $6.2M in space at the deadline if nothing else changes (but it will because Holmstrom is going to be recalled, so it'll probably be closer to $5.4M).
Contracts are paid out during the course of the season so as the season progresses the amount of money every player is owed decreases. When a player is acquired they're only owed what is remaining on their contract for the year and that's why teams accrue cap space. Using LTIR negates this cap space accrual though so teams try not do use that if they can avoid it.
As for injuries and whatnot, accrual depends on the type of injuries and whether or not a player will need to be placed on LTIR. We have seen teams try to accrue more space by doing paper transactions over recent years too. An example might be sending Holmstrom down to the minors (since he doesn't require waivers) for a stretch where the Islanders don't plan on using him but never having him physically report to Bridgeport. It drops the roster from 23 players to 22 players for a small duration and decreases the cap hit by ~$800K for a short period of time.
Absolutely. I think the phasing out should've happened when Johnston was re-signed to a multi-year deal before Martin was re-upped. At the time it seemed like that was the route they were heading but then reversed course a bit. My bigger issue is with the phasing out of Clutterbuck. Since he had multiple broken vertebrae I've thought they needed to start looking for new options. Maybe he's too important to the locker room for that but he's been a ticking time bomb ever since then (and the hand/wrist injury doesn't help either).