Yeah, I mean I've played ~1000 of matches with variants of this deck and I still find new lines of play and make errors. There are just so many decisions when you have the option to dredge back use-able cards and all the good flashback spells that I've tried over the years. If you've already gone through the effort of assembling the deck, I'd at least try tuning it to your preference.
You can probably cut a copy or two of Loam, but I wouldn't do that if your goal is to make Loam more reliable. You want as many copies of it as you can get if you are going to rely on it so I've been at 4 Loams for a couple of years now in most of my builds. The card doesn't actually take any real slots since its just competing with other dredgers. You can up the Dakmors and Portals by trimming some stuff like Chancellor, and Stinkweeds. That might not be the direction you want if you want to make it faster though.
Like I said, I don't think the deck is any slower because I don't think Bridge from Below helps with speed. It helps with resilience when you need to fight through counterspells, sphere, and other situations that are preventing you from comboing hard. Amalgam is the same speed as Ichorid so the creature count is overall the same, and the access to extra land drops makes up for the grind factor you lose with no Bridges. If you want to increase speed in a dredge deck, the only real route is Fatestichers, imo. Its the next best GY creature, other than Ghast and Narcomoeba, at coming out on turn 2. So playing through counterspells is the situations where it can be slower, this is roughly only 50% of match ups (since other people are on Shops/Dredge/Survival/Storm/other non-blue) and even in those match ups only about 50% of the time will they even have a counter for Return. So you are talking about 25% of the time that it might be slower. At the same time, I feel its faster in situations where Bridge from Below is unreliable, e.g. against a Ravager and the Dredge mirror, since this deck is already well prepared to play a game with no Bridge from Below. Based on meta %'s, I think that evens it out overall.
My current list:
I haven't been totally happy with it though so I've been tinkering with some of the numbers, and the sideboard.