Default route fail-over between BGP peers? (BFD questions)

Good morning! I just wanted to get some peoples opinions on what they would do/try in my situation to see if there's a better way to be doing this.

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I have an office site that has two routers, we will call them B1 and B2. These routers are connected to each other and running ibgp between them. B1 is also peered via ebgp with our ISP1, and getting a default route from the bgp peering. B2 is then also peered with ISP2 which is an IPVPN/L3VPN connection; also peered with ISP2 is our datacenter which is sending a default route into the "mpls" for other sites to use as backup internet.

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So pretty simple multihome setup: B1 connected to ISP1 and getting default via BGP, B2 connected to "MPLS" and getting default route from datacenter via BGP.

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But, right now failover is set up doing an IP SLA with a static route out to ISP 1. I inherited this network a couple years ago and I have been going through and slowly updating/optimizing/fixing all the patchwork routing - and this month is FailOver-January.

Is there a better way to be doing this? I was thinking BFD (assuming the DIA ISP supports it). But I have a few questions about BFD: 1) does BFD need to be configured on just the ISP1/Primary peer session, or on both? 2) if both does the multihome being on two different routers cause issues? 3) Is there an issue doing BFD on a peering with the ISP2 doing IPVPN when the peering is with the ISP but default is coming from the remote datacenter (2 hops away)?

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If BFD isn't the cream dream here, what else do people recommend? I can't get access to my networking lab for a couple weeks so hand jamming configs in excel for testing fun once I get back into an office.