Did you eventually recover the funds?
I have been trying to figure this out for over an hour, but still something doesn't seem to be right with the shitty Abra wallet. The foremost problem was with the KYC shits like knowing of names, email addresses and mobile numbers. Got passed through them by giving away fake numbers and stuffs but then as nc50lc pointed out, the custom derivation paths seems to be a major bullshit associated with Abra.
So thought of recreating the exact scenario like OP (sending btc to abra controlled bsv address) and all is that I lost $0.1 worth of btc in the progress
[1]Started with bypassing all the abra wallet kyc shits (like name and mobile numbers)
[2]Noted down the 12 word passphrase
[3]Sent $0.1 worth of bitcoin to BSV address displayed in the app
[4]Transaction had 1 confirmation in blockchain
[5]Created a new wallet in electrum, entered the seeds and tried out multiple combination of derivation paths (maybe more than 10)
[6]Generated over 20,000 addresses for each derivation paths using iancoleman's BIP39 tool
[6]None of them had a bsv wallet address (out of 200000 addresses) and finally lost the $0.1 worth of BTC
I am not really sure if the support team would respond back with a exact derivation path and another point is that they should never advertise their wallet like a 'non-custodial wallet' provided they have certain control on the wallet in the form of custom derivation paths!
Helping out in answering some queries to get going with the recovery
If the 13-word seed is BIP39.
Yes, derived twice and checked. They initially had 13 words but the first word is always 'at' which should be removed while entering the seed in Electrum.
Abra wallet's seed phrase isn't compatible with Electrum. I have tried creating a seed and import it into Electrum. Doesn't work.
They are indeed compatible. Remove the first word 'at' from the 13 word phrase and enter the remaining 12 words
There's no option to get private key of addresses as well.
If the support does respond with a custom derivation path, that should be the only way for recovery. But all is that they have a poor customer support which doesn't really know what we speak! Shady, controlling funds with derivation paths, shitty customer support, (I would never recommend OP to store his funds in future with this wallet)