Hi, the limit of ARP Table size could be a factor but, not knowing the number of clients currently present on your network and looking at static routes defined on each switch, I'm more inclined to think you should redesign your physical and logical topologies to (a) avoid a physical loop (if not necessary and if STP is not properly configured on all involved switches) and (b) avoid having more than one switch with routing role.
Point (a) could be easy to fix. Point (b) requires you to rethink your routing approach.
If I were you I will create/use a Transport VLAN (say a 10.10.1.0/30) created on Switch A (designated to be the Core router for all others switches B, C and D), assign the .1 to the VLAN 1 (VLAN 1 is not going to be necessary on all other switches) and the .2 to your Firewall's LAN interface (on its defined VLAN 1). On Switch A the Route of Last Resort 0/0 via Next Hop Gateway will become 0.0.0.0 0.0.0.0 via 10.10.1.2 and, viceversa, on your Firewall all 10.10.x.0/24 subnets will be reacheable via 10.10.1.1.
I will return to Layer 2 switch to switch (between A and B, C, D) carrying as tagged on the uplinks only VLANs that are exactly needed respectively on B, C and D.
I will check and, if needed, fix the STP so the A is going to have the highest STP priority to became root, I will leave all others with lower ones.
I will get rid of IP Routing on B, C and D. I will get rid of static routes on them (not necessary).
I will eventually define a VLAN (say 10.10.100.0/24 with VLAN id 100) to be used as Managment subnet and I will set an IP on that VLAN on A (say .1, B say .2, C say .3 and D say .4), the VLAN 100 will be transported (tagged or untagged) across A downlinks to B, C and D.
B, C and D will require only the Default Gateway settings to point to 10.10.100.1. Clients connected to A, B, C and D will require to have their D.G. set to point to respective VLAN SVI (all .1 on 10.10.x.1 where x=10, 20, 30, 40, and so on...).
The uplink on the Switch A Firewall could remain set as Access with PVID 1 (I mean: with VLAN 1 untagged on the link even if you can think of moving on an alternate dedicated VLAN and tag it, but you also need to make changes on the Firewall's LAN side to cope with that).